Wozniacki is the daughter of Polish immigrants, Piotr Woźniacki and Anna Woźniacka. Anna played on the Polish women's national volleyball team, and Piotr played professional association football. The couple moved to Denmark when Piotr signed for the Danish football club Boldklubben 1909. Her older brother, Patrik Wozniacki, is a professional footballer for IF Skjold Birkerød in Denmark.
Wozniacki's playing style centers on "the defensive aspects of tennis with her anticipation, movement, agility, footwork and speed all first-rate and key parts of her game." She also anticipate serves with aggressive footwork. Her two-handed backhand is one of her best weapons as she is capable of turning defense into offense, most notably the backhand down-the-line. Her defensive playing style has her contemporaries label her a counter-puncher.
In 2009, Wozniacki signed on to become an endorser for the line of tennis apparel designed by Stella McCartney for Adidas. She wore her first 'Adidas by Stella McCartney' tennis dress at the 2009 US Open. She currently has partnership agreements with Babolat, Rolex, Adidas, USANA, The Players' Tribune and Mundipharma. On 20 December 2010, she signed a three-year deal to endorse Turkish Airlines' business class service. In 2012, Wozniacki became an endorser of Compeed BlisterPatch. At the end of 2013 she switched her racquet sponsorship from Yonex back to her long-time partner Babolat. In 2015, Wozniacki became an endorser of Godiva Chocolatier.
According to the June 2011 edition of SportsPro Wozniacki is the world's ninth most marketable athlete. According to Forbes in 2011 Wozniacki was the second highest-earning female athlete in the world.
Wozniacki won several junior tournaments in 2005, including the Orange Bowl tennis championship. She made her debut on the WTA Tour at Cincinnati's Western & Southern Financial Group Women's Open on 19 July 2005, losing to the top-seeded and eventual champion Patty Schnyder in the first round. In the Nordea Nordic Light Open, her other WTA tournament of the year, she lost to Martina Suchá in the first round.
In 2006 she was the top seed at the Australian Open (junior girls' singles), but lost the final to eighth-seeded Anastasia Pavlyuchenkova. She was seeded second with partner Anna Tatishvili in the doubles tournament, but the pair was knocked out in the semifinals by the French-Italian pair of Alizé Cornet and Corinna Dentoni, who were seeded eighth. In February at the Memphis she reached her first WTA Tour quarterfinal, beating Kristina Brandi and Ashley Harkleroad, before losing to third-seeded Sofia Arvidsson of Sweden. Before Wimbledon Wozniacki won the Liverpool International Tennis Tournament, an exhibition tournament, beating Ashley Harkleroad in the final. Later that year she was given a wild card to the qualifying draw at Wimbledon, where she was beaten in the first round by Miho Saeki. However, Wozniacki went on to win the Wimbledon girls' singles tournament, beating Slovak Magdaléna Rybáriková in the finals. In August she reached another WTA Tour quarterfinal, this time at the Nordea Nordic Light Open in Stockholm. She defeated top-100 players Iveta Benešová and Eleni Daniilidou, before falling to eventual champion and third-seeded Zheng Jie. Wozniacki was seeded second in the US Open Girls' Singles in the last major tournament of 2006, US Open. In the first round, she won the first set against Russian Alexandra Panova, but was disqualified in the second set for verbally abusing an umpire. Wozniacki was said to have used an expletive in referring to a linesman who made a disputed call. However, on her blog, she claimed to have said, "take your sunglasses of [sic]" and was mistaken for talking to the linesman, when she in fact was criticizing herself after the next point. In her last junior tournament, the Osaka Mayor's Cup, she won both the girls' singles and doubles. Her first title on the senior tour came shortly after on 29 October, when she won the $25,000 International Tennis Federation (ITF) tournament in Istanbul by beating Tatjana Malek in the final. Wozniacki was set to face Venus Williams on 27 November in an exhibition match in Copenhagen, but five days before the event, Williams canceled because of an injury. The two did, however, face each other in the Memphis WTA Tier III event on 20 February. Williams beat Wozniacki, ending a nine-match winning streak for Wozniacki. On 29 November Wozniacki was named ambassador for Danish Junior Tennis by the Culture Minister of Denmark at the time, Brian Mikkelsen.
On 4 February 2007 she won a $75,000 ITF singles title in Ortisei, Italy, beating Italian Alberta Brianti. On 4 March she won the $75,000 ITF tournament in Las Vegas, beating top-seed Akiko Morigami in the final. She obtained a wild card for the Pacific Life Open main draw and made her Tier I debut there. She was knocked out in the second round by Martina Hingis. She then made the semifinals of the AIG Open in Tokyo in October, her first career WTA Tour semifinal, and as a result became the first Danish woman to reach a WTA semifinal since Tine Scheuer-Larsen at Bregenz in 1986. She was defeated by Venus Williams in straight sets.
At the Australian Open Wozniacki defeated Gisela Dulko and 21st seed Alona Bondarenko on her way to the round of 16, where she lost to the eventual finalist and fourth-seeded Ana Ivanovic. At the French Open Wozniacki was seeded 30th, making this the first Grand Slam tournament in which she was seeded. She again lost in the third round to the eventual champion and world No. 2 Ana Ivanovic. At Wimbledon she reached the third round, but lost to second-seeded Jelena Janković.
Wozniacki won her first WTA Tour title at the Nordic Light Open in Stockholm without dropping a set, defeating fifth seed Anabel Medina Garrigues in the quarterfinals, top seed and world No. 10 Agnieszka Radwańska in the semifinals, and Vera Dushevina in the final. At the Summer Olympics in Beijing she beat world No. 12 Daniela Hantuchová in the second round, before falling to the eventual gold-medalist Elena Dementieva. Wozniacki then won her second WTA Tour title at the Pilot Pen Tennis in New Haven, defeating three seeded players, Dominika Cibulková, Marion Bartoli, and Alizé Cornet, en route to the final, where she defeated world No. 11 Anna Chakvetadze. Wozniacki was the 21st seed at the US Open. She defeated world No. 14 Victoria Azarenka in the third round, but lost to second-seeded and eventual runner-up Jelena Janković in the fourth round. At the China Open she lost her opening match to Anabel Medina Garrigues. However, she teamed up with Medina Garrigues to clinch the doubles title, defeating the Chinese duo of Han Xinyun and Xu Yifan. It was Wozniacki's first WTA doubles title. At the Tier III AIG Japan Open Tennis Championships she was the top seed for the first time on the WTA Tour, and won her third career title, defeating Kaia Kanepi of Estonia in the final. Wozniacki then took part in the Nordea Danish Open, in her hometown of Odense. After a string of good performances, she won the tournament, beating world no. 64 Sofia Arvidsson of Sweden in the final.
Wozniacki's final win–loss record for the year (ITF matches included, exhibition matches not included) was 58–20 in singles and 8–9 in doubles. She ended the year ranked 12th in singles and 79th in doubles. She finished thirteenth in the race for the Sony Ericsson Championships. She also won the WTA Newcomer of the Year award for 2008.
Wozniacki started the season in Auckland, where she lost to Elena Vesnina in the quarterfinals. She also reached the quarterfinals in Sydney, this time losing to world No. 2 Serena Williams after having three match points. Seeded 11th at the Australian Open, Wozniacki lost in the third round to Australian wild card Jelena Dokić.
In Pattaya, Wozniacki lost to Magdaléna Rybáriková in the quarterfinals. Seeded first at the Cellular South Cup in Memphis, Tennessee, Wozniacki advanced to the final, but lost to Victoria Azarenka. Afterwards, they partnered in the doubles final to defeat Michaëlla Krajicek and Yuliana Fedak.
Wozniacki then took part in the first two Premier Mandatory tournaments of the year. At Indian Wells, she lost in the quarterfinals to eventual champion Vera Zvonareva. In Miami, she scored her first win over Elena Dementieva, before losing to another Russian Svetlana Kuznetsova in the quarterfinals.
Wozniacki won her first title of the year at the MPS Group Championships on green clay in Ponte Vedra Beach, where she defeated Canadian Aleksandra Wozniak. In Charleston, she defeated top seed Elena Dementieva in the semifinals, before losing the final to Sabine Lisicki.
Wozniacki suffered early exits in her next two tournaments, losing to Marion Bartoli in the second round in Stuttgart, and to Victoria Azarenka in the third round in Rome. She reached the final of the inaugural Premier Mandatory Mutua Madrileña Madrid Open, where she lost to world No. 1 Dinara Safina. This was Wozniacki's only match against a reigning No. 1 before she herself became No. 1 in October 2010. Seeded 10th at the French Open, Wozniacki lost to Sorana Cîrstea in the third round. They partnered in doubles, but lost in the first round.
Wozniacki won her second 2009 title on the grass of Eastbourne. In the final, she defeated Virginie Razzano. Wozniacki was seeded ninth at Wimbledon, where she lost to Sabine Lisicki in the fourth round.
On her 19th birthday, she lost the final of the Swedish Open to María José Martínez Sánchez. On hard court at the LA Women's Tennis Championships, she lost in the second round to Sorana Cîrstea. At the Cincinnati Masters, she reached the quarterfinals, before falling to Elena Dementieva. In Toronto, she lost early in the second round to Zheng Jie, but she then went on to defend her title at the Pilot Pen Tennis in New Haven without losing a set. In the first round, she had her first double bagel win as a professional, 6–0, 6–0, over Edina Gallovits in 41 minutes. In the final, she beat Elena Vesnina for her third title of the season.
Wozniacki was the ninth seed at the US Open. She made her best result to date by becoming the first Danish woman to reach a Grand Slam final. Her route to the final included a hard-fought three-set win against reigning French Open champion Svetlana Kuznetsova in the fourth round before scoring straight sets win against Melanie Oudin in the quarterfinals and Yanina Wickmayer in the semi-finals. There, she was defeated by Kim Clijsters, who had recently made a comeback after retiring in 2007, despite serving for the 1st set.
In the second round of the Toray Pan Pacific Open, she retired because of a viral illness down 0–5 against Aleksandra Wozniak. She then lost to María José Martínez Sánchez in the first round of the China Open, and to Samantha Stosur in the semifinals in Osaka. The following week in Luxembourg, she retired with a hamstring injury in the first round, while leading 7–5, 5–0 over Anne Kremer. This aroused controversy because of the scoreline.
Wozniacki's stellar 2009 results qualified her for the year-end Sony Ericsson Championships in Doha for the first time. She won two of three group matches and advanced to the semifinals. There she struggled with a stomach strain and a left thigh injury against world No. 1 Serena Williams, and retired while trailing 6–4, 0–1.
In her first WTA tournament of the year, Wozniacki suffered an opening-round loss to Li Na of China in the Sydney. She was seeded fourth at the Australian Open, her first top-eight seed in a Grand Slam. She again fell to Li, this time in the fourth round, in straight sets. Despite her fourth-round exit, Wozniacki achieved a career-high ranking of no.3.
As the second seed at Indian Wells, Wozniacki reached the final before losing to former world No. 1 Jelena Janković. With this result, she achieved a new career-high ranking of world no.2. At the Sony Ericsson Open in Miami, Wozniacki lost in the quarterfinals to the newly returned Justine Henin.
Her next tournament was in Ponte Vedra Beach, where she defeated Olga Govortsova in the final. Wozniacki then competed at the Family Circle Cup in Charleston. She advanced to the semifinals, where she met Vera Zvonareva. Wozniacki was forced to retire down 2–5, after she rolled her ankle while chasing down a short ball.
Despite her ongoing ankle injury, she continued to compete in tournaments through the clay-court season, suffering early losses in Stuttgart, Rome, and Madrid. She then reached the quarterfinals in Warsaw, but retired there after losing the first set.
Wozniacki was seeded third at the French Open. She posted her best result at Roland Garros by advancing to the fourth round without dropping a set. After defeating Flavia Pennetta in the round of 16 in three sets, she lost to eventual champion Francesca Schiavone in the quarterfinals. Wozniacki partnered with Daniela Hantuchová in doubles, but they withdrew before their second round match against the Williams sisters because of a right shoulder injury to Hantuchová.
As the defending champion, Wozniacki lost early at the Aegon International, her first grass-court tournament of the year, to Aravane Rezaï. Wozniacki was seeded third at Wimbledon, where she defeated Tathiana Garbin, Chang Kai-chen, and Anastasia Pavlyuchenkova en route to the fourth round, where she was defeated by Petra Kvitová.
Wozniacki was the first seed at the inaugural e-Boks Danish Open. It was the first Danish WTA tournament, created largely out of Wozniacki's popularity in Denmark. She reached the final, and she defeated Klára Zakopalová to win her second title of the year.
In Cincinnati, she lost in the third round to Marion Bartoli. As the second seed in Montreal, Wozniacki was forced to wait two days to play her semifinal match with Svetlana Kuznetsova because of heavy rain. She defeated both Kuznetsova and Vera Zvonareva on the same day for her third singles title of the year. As the top seed in New Haven, Wozniacki defeated Nadia Petrova in the final for her third consecutive title there. By virtue of this, she also won the US Open Series.
Wozniacki was the top seed at the US Open due to the withdrawal of world No. 1 Serena Williams. She advanced to the semifinals, before being upset by Vera Zvonareva. With her semifinal appearance, Wozniacki became one of only two women (the other being Venus Williams) to have reached at least the fourth round of all four Grand Slam events in 2010.
Wozniacki's first tournament during the Asian hard-court season was the Toray Pan Pacific Open in Tokyo. She won back-to-back three setters against Victoria Azarenka and Elena Dementieva, the latter of whom she beat in the final to win her fifth title of the year.
She then entered the China Open in Beijing. In the third round, Wozniacki faced Petra Kvitová, who had routed her at Wimbledon. Wozniacki avenged that loss, which ensured that she would replace Serena Williams as the new world No. 1 after the tournament. She was the fifth player to reach the No. 1 position without having won a Grand Slam tournament. She also became the first Danish player, man or woman, to reach the top ranking. Wozniacki ultimately won the tournament, defeating Vera Zvonareva in the final to win her sixth title of the year and twelfth overall.
At the year-end Sony Ericsson Championships in Doha, Wozniacki was drawn in a group with Francesca Schiavone, Samantha Stosur, and Elena Dementieva. She defeated Dementieva in her first round-robin game, but lost to Stosur in the second. She won her last round-robin match in the group against Schiavone, securing the year-end world no.1 rank and a place in the semifinals against the winner of the other group, Vera Zvonareva. Wozniacki defeated her, but then lost the final in three sets to Kim Clijsters. Wozniacki ended the season with six WTA singles titles, the most on the tour. Clijsters won five, and no other player won more than two.
During the off season, Wozniacki switched her racquet make from Babolat to Yonex. Wozniacki began her 2011 season with an exhibition match in Thailand against Kim Clijsters where she lost in a super tie-break. Wozniacki then played another exhibition, the team Hong Kong Tennis Classic, where she represented and was captain of Team Europe. She won two matches against Team Asia Pacific, before getting crushed by world No. 2 Vera Zvonareva in the final against Team Russia. Her first WTA tournament was the Medibank International Sydney. She received a bye to the second round, where she lost to Dominika Cibulková.
The Australian Open was Wozniacki's first major as world no. 1. She lost to Li Na in the semifinals after failing to convert a match point when trying to serve out the match at 5–4 in the second set.
Wozniacki dropped to No. 2 behind Kim Clijsters during the week of 14 February, but regained the top spot the following week. She received a bye to the second round in Dubai where, in the quarterfinals, she beat Shahar Pe'er to ensure her No. 1 position in the next rankings update. She went on to defeat Svetlana Kuznetsova in the final to take her 13th career singles title and first of the year. In Doha, she received a bye to the second round and reached the final, after defeating Nadia Petrova, Flavia Pennetta, and Marion Bartoli in straight sets. She lost to Vera Zvonareva in the final. In the first Premier Mandatory event of the year in Indian Wells, Wozniacki made it to the final, where she defeated Marion Bartoli for her 14th singles title. After a first-round bye at the Sony Ericsson Open in Miami, Florida, Wozniacki lost in the fourth round to 21st seed Andrea Petkovic. Wozniacki made an uncharacteristic 52 unforced errors and later said she had been playing a lot of matches when she was asked about fatigue. In the Family Circle Cup, Wozniacki made it to the final, where she defeated unseeded Elena Vesnina to take her third title of the year, 15th of her career. In Stuttgart, Wozniacki made it to her fifth final of the year, where she lost to Julia Görges in straight sets. In Madrid, Wozniacki lost to Görges again, this time in the third round. In Rome, she lost to eventual champion Maria Sharapova in the semifinal round. At the Brussels Open, Wozniacki reached the semifinals, where she defeated third seed and reigning French Open champion, Francesca Schiavone. In the final, Wozniacki's sixth of the year, she defeated eighth seed Peng Shuai to win her first red clay title, after having won three on the faster green clay. Wozniacki was the top seed at the French Open, but was defeated in the third round by 28th seed Daniela Hantuchová.
Wozniacki's next tournament was the e-Boks Sony Ericsson Open in her native Denmark. In the final, she defeated fourth seed Lucie Šafářová, taking her fifth title of the year. At Wimbledon, she had straight-set wins until the fourth round, but then lost to 24th seed Dominika Cibulková.
At the Rogers Cup Wozniacki made an early second-round exit. She was defeated by Roberta Vinci in straight sets despite holding a 5–1 lead in the second set. Wozniacki was the top seed at the Western & Southern Open in Cincinnati, but lost in the second round to world No. 76 Christina McHale. Next playing at the New Haven Open at Yale, Wozniacki won the title for the fourth year in a row, defeating Francesca Schiavone in the semifinals and qualifier Petra Cetkovská in the final.
At the US Open, Wozniacki was the first seed. In the first round, she defeated Nuria Llagostera Vives. In the second round, Wozniacki defeated Arantxa Rus, and in the third round, defeated American Vania King. In the fourth round, Wozniacki fought back from a 7–6, 4–1 deficit, defeating Svetlana Kuznetsova. Wozniacki then progressed to the semifinals by defeating Andrea Petkovic in the quarterfinals. In the semifinals she lost to Serena Williams.
In Tokyo Wozniacki lost to Kaia Kanepi in the third round. In Beijing she lost to Flavia Pennetta in the quarterfinals. This was Wozniacki's only loss in the 12 quarterfinals she reached in 2011.
Wozniacki was the top seed at the WTA Championships. In the group stage she beat Agnieszka Radwańska before falling to Vera Zvonareva. She lost also to Petra Kvitová in her final round-robin match and so she failed to advance to semifinals for the first time in three appearances. She finished the year as world No. 1 for the second consecutive year. Despite narrowly edging Petra for the Year End No. 1 ranking in points, she lost out on all Player of Year awards to Petra.
Wozniacki began her season by representing Denmark at the 2012 Hopman Cup with Frederik Nielsen as her partner. Wozniacki won two of her three round robin matches in singles, defeating Bethanie Mattek-Sands and Tsvetana Pironkova before losing to world No. 2 Petra Kvitová.
Wozniacki's first WTA event was the Apia International Sydney. After a first round bye, Wozniacki defeated Dominika Cibulková after trailing 4–0 in the third set. She lost to Agnieszka Radwańska in three sets in the quarterfinals, after serving for the match at 5–4 up in the second set.
Wozniacki competed at the Australian Open as the top seed. She defeated Anastasia Rodionova, Anna Tatishvili, Monica Niculescu, and Jelena Janković, all in straight sets, to reach the quarterfinals where she lost to the defending champion Kim Clijsters. As a result, Wozniacki lost her top ranking and was replaced by the 2012 champion Victoria Azarenka. Next playing at Doha, Wozniacki lost to Lucie Šafářová in the second round, having received a first round bye.
Wozniacki was the defending champion in Dubai and Indian Wells, but failed to defend either title, losing to Julia Görges and Ana Ivanovic, respectively.
Wozniacki reached the semifinals in Miami after beating Barbora Záhlavová-Strýcová, Petra Cetkovská, Yanina Wickmayer, and Serena Williams, all in straight sets. Wozniacki then lost to second seed Maria Sharapova. Wozniacki did not defend her title in Charleston as she was not allowed to participate under WTA rules because two top-6 players had already entered the draw. Wozniacki then played her home tournament in Copenhagen. She reached the final but lost to Angelique Kerber, her first loss at the tournament since the start in 2010.
Wozniacki reached the third round of the French Open, where she lost to Kaia Kanepi in three sets.
Wozniacki lost in the first round of Wimbledon to Austrian Tamira Paszek. It was her first opening-round exit from any Grand Slam since making her professional debut at the 2007 French Open.
Wozniacki represented Denmark at the Olympics as the eighth seed in the women's singles event. In the first three rounds she defeated Anne Keothavong, Yanina Wickmayer and Daniela Hantuchová. She was then defeated by the eventual champion Serena Williams in the quarterfinals.
Wozniacki next participated in the Rogers Cup where she lost to Petra Kvitová in the semifinals, and the Western & Southern Open where she was defeated in the third round by Anastasia Pavlyuchenkova. As the four-time defending champion at the New Haven Open at Yale, Wozniacki retired against Maria Kirilenko in the semifinals due to a right knee injury, which she had suffered in her quarterfinal win over Dominika Cibulková.
Wozniacki, still suffering with the injury, was seeded eighth at the US Open, but did not advance past the first round. She lost in two sets to 96th-ranked Romanian Irina-Camelia Begu. As a result of the loss, Wozniacki dropped out of the top 10 for the first time in three years.
Following her US Open disappointment, Wozniacki won her first tournament of the year in Seoul by defeating Arantxa Rus, Caroline Garcia, Klára Zakopalová, Ekaterina Makarova, and Kaia Kanepi in the final. It was her 19th career title.
Wozniacki's next tournament was the Toray Pan Pacific Open in Tokyo. She defeated Bojana Jovanovski, Daniela Hantuchová and Li Na, before losing to Agnieszka Radwańska in the quarterfinals.
At the China Open in Beijing, Wozniacki defeated Chanelle Scheepers and Hsieh Su-wei but lost to Angelique Kerber in the third round.
Wozniacki's next tournament was the Kremlin Cup. As the third seed in the tournament, she defeated top seed Samantha Stosur in the final in 3 sets to take home her second title of the year, and 20th overall.
At the year-end Tournament of Champions in Sofia, Wozniacki won her three group matches and reached the final but lost to Nadia Petrova. She ended the year ranked 10th.
In December 2012, during an exhibition match in Brazil, Wozniacki imitated friend and fellow tennis player Serena Williams by stuffing towels in her shirt and skirt in order to appear to be large-chested and have a large rear end. This act divided opinion on social network sites. It was noted that Wozniacki has done the impression before without controversy. Williams also defended Wozniacki in an email to USA Today and pointed out that they are friends and that the act was not racist. Williams added however, that if people feel this way then she should do something else next time.
Wozniacki began the year in Brisbane where as the eighth seed, she lost in the first round to qualifier Ksenia Pervak in three sets. Wozniacki then competed at the Apia International Sydney. She defeated Urszula Radwańska but lost to Svetlana Kuznetsova in the second round. At the Australian Open, Wozniacki defeated Sabine Lisicki, Donna Vekić and Lesia Tsurenko, but once again lost to Kuznetsova, this time in the fourth round.
Wozniacki's next tournament was the Qatar Total Open where she reached the quarterfinals with wins over Mervana Jugić-Salkić, Sorana Cîrstea, Mona Barthel, before losing to Agnieszka Radwańska. In Dubai, Wozniacki defeated Lucie Šafářová, Zheng Jie and Marion Bartoli to reach the semi-finals where she lost to the eventual champion, Petra Kvitová. At the Malaysian Open she lost in the first round to Wang Qiang. She then played in an exhibition match at the BNP Paribas Showdown in Hong Kong. She was originally scheduled to play Li Na, but she had to withdraw due to injury. Instead Wozniacki played Li's replacement world No. 4 Agnieszka Radwańska and lost in straight sets.
At the BNP Paribas Open, she defeated Alizé Cornet, Elena Vesnina and Nadia Petrova before receiving a walkover the defending champion Victoria Azarenka, after the latter withdrew due to a foot injury. In the semi-finals, Wozniacki defeated Angelique Kerber to reach her first final of the year but lost the title match to Maria Sharapova. In her next tournament, the Sony Open in Miami, Wozniacki made it to the third round where she lost to Garbiñe Muguruza.
Wozniacki began the clay court season by reaching the quarterfinals of the Family Circle Cup where she lost to Stefanie Vögele. After this tournament, Wozniacki lost in the first round to Carla Suárez Navarro in Stuttgart, to Yaroslava Shvedova in Madrid, to Bojana Jovanovski in Rome, and to Zheng Jie in Brussels. At the French Open, Wozniacki defeated Laura Robson in the first round, before once again losing to Jovanovski in the second.
Wozniacki began her grass court season at the Aegon International in Eastbourne. She reached the semifinals after victories over Tamira Paszek, Laura Robson and Ekaterina Makarova but then lost to qualifier Jamie Hampton. In the first round of Wimbledon, Wozniacki beat Estrella Cabeza Candela. In the second round, she faced Petra Cetkovská. In just the fourth game of the first set, with the score at 2–1 and going with serve, Wozniacki slipped and fell, injuring her ankle. She received treatment but was visibly struggling and went on to lose the match. Wozniacki was one of several players to slip and injure themselves, including Jo-Wilfried Tsonga, Victoria Azarenka and Maria Sharapova. After the match, Wozniacki questioned whether the preparation for the tournament was the same as in previous years, adding: "I just know that it's just not really fun to be out there when you feel like you can't really push off on your foot."
Wozniacki's woeful season continued at the Rogers Cup, where she fell in the second round to Sorana Cîrstea despite having double match point in the second set. She then reached the quarterfinals of the Western & Southern Open, beating Peng Shuai, Monica Niculescu and Petra Kvitová, but was defeated by Victoria Azarenka for the first time since 2009. Wozniacki then played at the New Haven Open at Yale. She reached the semifinals beating Peng via retirement, Karin Knapp and Sloane Stephens before losing to Simona Halep in straight sets. At the US Open, Wozniacki defeated Duan Yingying and Chanelle Scheepers in straight sets before losing to qualifier Camila Giorgi in the third round. This marked the first time since 2008 where Wozniacki had failed to reach the quarterfinals or better at one of the four grand slam tournaments.
During the Asian swing, Wozniacki advanced to the semi-finals of the Toray Pan Pacific Open, defeating Flavia Pennetta, Magdaléna Rybáriková and Lucie Šafářová en route before losing to Angelique Kerber. Her next tournament was in Beijing where she was seeded sixth and where she received a bye into the second round along with the other three Tokyo semi-finalists. Wozniacki reached the quarterfinals after wins over Monica Niculescu and Sloane Stephens, but lost to the world No. 1 and eventual champion, Serena Williams.
Wozniacki's final event for the year was the BGL Luxembourg Open, where she was seeded first. She ended her two-match losing streak against Bojana Jovanovski by defeating the Serb in a three set quarterfinal before beating Wimbledon finalist Sabine Lisicki to reach the final where she defeated Annika Beck of Germany in straight sets to win her first and only title of the year. Despite the victory, Wozniacki failed to qualify for the year-ending WTA Tour Championships in Istanbul as Angelique Kerber secured the final spot with her win at the WTA International tournament in Linz, Austria that same week. In winning Luxembourg however, Wozniacki qualified for the WTA Tournament of Champions in Sofia but ultimately chose not to participate. She finished the year ranked world No. 10.
During the off season, Wozniacki switched her racquet make from Yonex to Babolat. She was scheduled to start the season in Brisbane but withdrew due to a right shoulder injury and instead began her season in Sydney where she defeated Julia Görges in three sets, before falling to Lucie Šafářová in the second round. At the Australian Open, she lost to Garbiñe Muguruza in the third round in three sets.
After the Australian Open, Wozniacki competed at the Qatar Total Open where she was seeded eighth and where she lost to Belgian Yanina Wickmayer after a first round bye. The following week, she reached the semi-finals in Dubai, defeating Sabine Lisicki, Annika Beck and Sorana Cîrstea before falling to the eventual champion Venus Williams.
Wozniacki's next tournament was the BNP Paribas Open where she was defending runner-up points. She reached the fourth round following wins over Bojana Jovanovski and Yaroslava Shvedova, before losing to Jelena Janković, causing her to fall to World No. 18, her lowest ranking since 2010. She recovered by reaching the quarterfinals of the Sony Open, recording wins over Monica Puig, Sloane Stephens and Varvara Lepchenko before losing to Li Na in a tight straight sets match. Wozniacki then made her debut at the Monterry Open, where she defeated Coco Vandeweghe, Kristina Mladenovic and Karolína Plíšková en route to the semifinals, before losing to the eventual champion Ana Ivanovic.
Her first tournament of the clay court season was scheduled to be the Porsche Tennis Grand Prix, but she was forced to withdraw due to a left wrist injury. Instead, her first event on clay was the Mutua Madrid Open where she reached the second round after beating Ekaterina Makarova before losing to Roberta Vinci after sustaining a knee injury. This same injury caused her to withdraw from the following week's Internazionali BNL d'Italia in Rome. At the French Open, Wozniacki was upset by Yanina Wickmayer in the first round in three sets.
Wozniacki enjoyed a stellar grass court season during which she made the semi-finals of the Aegon International with wins over Samantha Stosur, Sloane Stephens and Camila Giorgi before losing to the eventual finalist Angelique Kerber. At the Wimbledon Championships, Wozniacki reached the fourth round for the fourth time in her career after straight sets wins over Shahar Pe'er, Naomi Broady and Ana Konjuh but ultimately lost to Barbora Záhlavová-Strýcová.
After Wimbledon, Wozniacki won her first title of the year at the İstanbul Cup. She inflicted a double bagel on Belinda Bencic before defeating Karin Knapp, Karolína Plíšková and Kristina Mladenovic to reach the final where she dropped just two games in defeating second seed Roberta Vinci to secure the title.
Wozniacki's first tournament of the 2014 US Open Series was the Rogers Cup. She progressed to the quarterfinals after having straight set wins over Daniela Hantuchová, Klára Koukalová and Shelby Rogers before losing to top seed erena Williams, despite having led by a set and a break. At the Western & Southern Open, Wozniacki easily dismantled Magdaléna Rybáriková and Zhang Shuai before recording her first two top ten victories of the year by defeating Angelique Kerber in the third round and Agnieszka Radwańska in the quarterfinals. In the semifinals, she fell in three sets to the eventual champion Serena Williams.
Wozniacki's next tournament was the US Open, where she was the tenth seed. She faced Magdaléna Rybáriková in her opening match, progressing after her opponent was forced to retire early in the third set. She then beat qualifier Aliaksandra Sasnovich in the second round in straight sets. In the third round she easily took care of eighteenth seed Andrea Petkovic in straight sets for her first win over a seeded player at a grand slam since 2012. In the fourth round, Wozniacki came up against former world number 1 and former champion Maria Sharapova, defeating her in three sets to progress to the quarterfinals of a grand slam for the first time since the 2012 Australian Open. In the quarterfinals, she dropped just one game to breeze past Sara Errani. In the semifinals, Wozniacki came up against unseeded Peng Shuai. Wozniacki was up a set when her opponent was forced to retire due to a severe heat-related illness, allowing Wozniacki to advance to her second grand slam final, and her first since the 2009 US Open. In the final, Wozniacki came up against two-time defending champion Serena Williams for the third time in four weeks, again falling to the world number 1. Due to her run to the final, Wozniacki returned to the top 10 for the first time since February.
During the fall, Wozniacki competed at the Toray Pan Pacific Open. As the second seed, she received a bye into the second round where she faced Australian qualifier Jarmila Gajdošová. Wozniacki rallied from a set down to prevail. In the quarterfinals, she faced Carla Suárez Navarro, whom she easily defeated to progress to the semifinals. In a gruelling match against unseeded Spaniard Garbiñe Muguruza whom she had never beaten before, Wozniacki won in three sets to set up a clash with Ana Ivanovic. In her third final of the year, Wozniacki fell to the Serbian in straight sets. Wozniacki's next tournament was the Wuhan Open. As the eighth seed, she received a bye into the second round, where she defeated Carla Suárez Navarro in three sets. Wozniacki then beat Casey Dellacqua and Timea Bacsinszky to reach the semifinals where she lost to Eugenie Bouchard in straight sets.
The following week, she competed at the China Open where she received a bye into the second round due to being a semifinalist in Wuhan. She was eliminated by Samantha Stosur in her opening match of the tournament. It was then announced on 2 October that Wozniacki had qualified for the WTA Finals.
At the WTA Finals, Wozniacki was drawn into the White Group alongside Maria Sharapova, Petra Kvitová, and Agnieszka Radwańska. In her first match she beat Maria Sharapova in three sets. She then went on to beat Agnieszka Radwańska in straight sets. With Sharapova winning in three sets against Radwańska, Wozniacki qualified into the semifinals. She then beat Petra Kvitová in straight sets going undefeated in her round robin matches. She would lose to Serena Williams in the semifinals in three sets despite serving for the match in the third set and leading 4–1 in the third set tiebreak. She finished the year ranked at No. 8.
Wozniacki then decided to run the New York City Marathon on 2 November 2014. She recorded a time of 3 hours, 26 minutes and 33 seconds. She claimed that the running training has been positive for her and has contributed to her good performances at the US Open and WTA Finals.
Wozniacki started her preparation for the Australian Open at the ASB Classic in Auckland seeded as No. 1 and advanced to the final before losing to Venus Williams in three sets. Despite being seeded eighth at the Australian Open, Wozniacki was unfortunate to draw fellow former world number one and two-time champion Victoria Azarenka in the second round, and was defeated in straight sets. After the tournament, she climbed back up to no.5. Wozniacki then competed at the Dubai Tennis Championships where she made it all the way to the semifinals before losing to eventual champion Simona Halep in three sets. Wozniacki's next tournament was the Qatar Total Open where she was seeded second. However, she lost once again to fellow former No. 1 Victoria Azarenka in the quarterfinals in straight sets, winning just four games. She rebounded at the Malaysian Open, winning the title by defeating Romanian Alexandra Dulgheru in the final in three sets.
Wozniacki's next tournament was the BNP Paribas Open where she was seeded fourth. In the second round, she beat Ons Jabeur before losing in the third round to Belinda Bencic in straight sets. She then competed at the Miami Open beating Madison Brengle in the second round and Kaia Kanepi in the third round. She lost to Venus Williams in the fourth round in straight sets.
Wozniacki started her clay season in Stuttgart where she was seeded fourth. In the second round, she beat Lucie Šafářová in straight sets. In the quarterfinals, she dropped just three games against Carla Suárez Navarro to advance to the semifinals. In the semifinals, she beat Simona Halep in a three set thriller to reach her first clay court final since 2011. She lost to Angelique Kerber in the final in three sets, despite serving for the match in the third set. Wozniacki's next tournament was the Mutua Madrid Open where she made it to the quarterfinals for the first time since 2009 beating Jarmila Gajdošová, Christina McHale, and Agnieszka Radwańska. She lost in the quarterfinals to Maria Sharapova in three sets. Wozniacki's next tournament was the Internazionali BNL d'Italia. She lost in the second round to Victoria Azarenka for the third time in straight sets. Wozniacki then played at the French Open as the fifth seed. She beat Karin Knapp in straight sets before losing to Julia Görges in the second round in straight sets.
Wozniacki started her grass season at the Aegon International. She beat Jarmila Gajdošová in straight sets and Svetlana Kuznetsova in three sets to advance to the quarterfinals. She beat Andrea Petkovic in straight sets to advance to the semifinals where she faced Belinda Bencic. She retired from the match due to a back injury after losing the first three games. Wozniacki then played at Wimbledon as the fifth seed. She beat Zheng Saisai in straight sets after being down 1–4 in the first set. After beating Denisa Allertová, she breezed past Camila Giorgi to advance to the fourth round and lost to eventual finalist Garbiñe Muguruza in straight sets. Despite the loss, Wozniacki climbed back up to No. 4 after the tournament.
Wozniacki's summer hard court season got off to a slow start due to an ankle injury. This injury caused her to lose early at Stanford, Toronto and Cincinnati to Varvara Lepchenko, Belinda Bencic and Victoria Azarenka, respectively. Wozniacki then played at the Connecticut Open. She finally picked up her first win by crushing Alison Riske in the first round. She then beat Roberta Vinci in three sets after being down 3–5 in the third set, saving 3 match points in the third set tiebreak, to advance to the quarterfinals. She breezed past Caroline Garcia before losing in the semifinals to Petra Kvitová in straight sets. Wozniacki then played at the US Open as the fourth seed. She easily beat Jamie Loeb in her opening match to advance to the second round where she was upset by Petra Cetkovská in a close three set match despite having four match points.
Wozniacki began her Asian hard court swing at the Toray Pan Pacific Open. As the top seed, she received a bye in to the second round where she easily beat Ana Konjuh. She then defeated Angelique Kerber in three sets in the quarterfinals. In the semifinals, she lost to Belinda Bencic for the fourth straight time in straight sets. Wozniacki's next tournament was the Wuhan Open. She lost to Anna Karolína Schmiedlová in the second round in three sets, despite being up a set and a break. Wozniacki's next tournament was the China Open. She beat Bojana Jovanovski in the first round, and won ten games in a row to beat Qiang Wang to advance to the third round. She lost to Angelique Kerber in straight sets. The loss ended Wozniacki's chances to qualify for the WTA Finals.
Wozniacki's next tournament was the Generali Ladies Linz. She beat Mirjana Lučić-Baroni in three sets before losing to Kirsten Flipkens in the second round in straight sets. Wozniacki failed to qualify for the WTA Finals, but she did qualify for the WTA Elite Trophy.
At the WTA Elite Trophy, Wozniacki was drawn into Group D alongside Roberta Vinci and Svetlana Kuznetsova. After retiring in her first match against Svetlana Kuznetsova, Wozniacki withdrew from the tournament. She finished the year ranked at No. 17, her worst year-end ranking since 2007.
Wozniacki began her 2016 season at the ASB Classic in Auckland, where she was defending finalist points. After beating Danka Kovinić in straight sets, she dropped a combined three games against Christina McHale and Alexandra Dulgheru to advance to the semifinals where she lost to eventual champion Sloane Stephens in straight sets. Wozniacki's next tournament was the Australian Open where she lost to Yulia Putintseva in the first round in three sets, marking her worst performance at the tournament. Wozniacki's next tournament was the St. Petersburg Ladies' Trophy. She lost to Dominika Cibulková in the second round in straight sets. Wozniacki next played the Qatar Open for which she needed 9 match points to beat Ana Konjuh in the first round. She was at one point up by a double break in the third set. In the second round, she faced Daria Gavrilova which she won in straight sets. Wozniacki then played Elena Vesnina in the third round, she fell in a grueling match. Wozniacki played in the Monterrey Open instead of defending her title in Kuala Lumpur. She defeated Olga Govortsova in the first round and Mirjana Lucic-Baroni in the second round; however, she fell in the quarterfinals to the eventual winner Heather Watson. Caroline then played at the BNP Paribas Open and fell in the second round to Zhang Shuai. This match marked the longest match so far in 2016, at 3 hours and 24 minutes. Then in the Miami Open Wozniacki made a promising start, defeating Vania King; however, she fell to twelfth seed Elina Svitolina.
Wozniacki was scheduled to play many clay court tournaments. However, she injured her ankle during a practice, which put her out for all of the clay-court season. This break saw Wozniacki fall though the rankings from 22 down to 34, the lowest since May 2008. She withdrew from French Open because her ankle was not 100%.
Wozniacki played in Nottingham, her first tournament since the Miami Open in March and her first tournament after hiring her new coach David Kotyza. Wozniacki won her first match in ten weeks defeating Çağla Büyükakçay, but falling in yet another three-set match to Anett Kontaveit in the second round. In her last tournament leading up to Wimbledon, Wozniacki played the Aegon International Eastbourne. She showed signs of improvement from her loss of form and injury, dismissing Alizé Cornet and seventh seed Samantha Stosur and dropping only seven games in the two matches before losing in a three-set match to qualifier Monica Puig. In Wimbledon, she went unseeded in the tournament, the first time since 2008 Australian Open and lost to Svetlana Kuznetsova in the first round, resulting in her falling out of the top 50 for the first time since February 2008.
Wozniacki began her US hard court season in Washington, playing the Citi Open she went on to beat Hiroko Kuwata in the first round and retired in her second round clash with Samantha Stosur despite being up a set 7–5 a sharp pain in her left arm forced her to retire. This injury also took her out of The Rogers Cup. She then played the Summer Olympic Games. Dropping four games she beat Lucie Hradecka but fell to Czech Petra Kvitová in the second round. She failed to win a match in the Connecticut Open as she lost in the first round to young Latvian Jelena Ostapenko. However, Wozniacki's year turned around at the US Open. She slid past Taylor Townsend in three sets, then upset Svetlana Kuznetsova in round two after being two breaks down she came back to win in straight sets. She then beat Monica Niculescu in two sets to reach the fourth round, in which she upended Madison Keys in two sets to reach the quarterfinals and then beat unseeded Anastasija Sevastova to enter the semifinals. Wozniacki lost the semifinal to then-new No. 1 Angelique Kerber, in two sets, and resulting at the back of the top 30 for the first time since April of this year.
Wozniacki moved on to the Toray Pan Pacific Open. In the first round, Wozniacki defeated Belinda Bencic, who had defeated her the previous year, in three sets. In the second round, she defeated fourth seed Carla Suarez Navarro, then beat qualifier Magda Linette in straight sets. In the semifinals, Wozniacki defeated defending champion Agnieszka Radwanska, which sent her off to her first final since April of the previous year. In the final, she defeated Japanese player Naomi Osaka to win her 24th WTA title, and her first title since March 2015. This was also Wozniacki's first Premier-level title since 2012.
Wozniacki continued the Asian swing at the Wuhan Open. There, she had a good start, defeating Samantha Stosur in the first round. In the third round, Wozniacki faced Agnieszka Radwanska again, and this time, Radwanska came out on top. Wozniacki then competed at the China Open. She cruised past her first two matches against Coco Vandeweghe and Roberta Vinci before going head to head with Radwanska for the third time in three weeks. Radwanska emerged victorious again, defeating Wozniacki in straight sets.
To finish off the Asian leg, Wozniacki partook in the Hong Kong Open. Seeded No. 5, she passed the first rounds easily, defeating Zheng Saisai, Heather Watson, and Wang Qiang. After beating Jelena Jankovic in the semifinals, Wozniacki won her 2nd title of the season and 25th title overall, beating Kristina Mladenovic in the final in three sets. This was the first time since 2012 that Wozniacki had won two WTA titles in a single season. With the win, Wozniacki returned to the top 20.
Wozniacki ended the season with a run at the Luxembourg Open. The No. 2 seed had an easy first round win against Madison Brengle, and survived a second round encounter against Sabine Lisicki after losing the first set. She then was forced to retire in the quarterfinals due to sickness. Wozniacki did not play at the WTA Elite Trophy and ended her topsy turvy season ranked No. 19 (having been as low as No. 74).
Wozniacki began the year at the Auckland Open once again. This time, she was the no.3 seed. She started out strong, breezing past Nicole Gibbs and Varvara Lepchenko before losing in the quarterfinals Julia Görges in three sets, despite being up a set and a break. At the Apia International Sydney, Wozniacki was seeded 10th. She played some solid tennis against Olympic Gold Medallist Monica Puig, winning in three sets. Wozniacki then defeated Yulia Putintseva in straight sets in a rematch of their 2016 Australian Open first round clash. In the quarterfinals, Wozniacki was defeated by Czech Barbora Strycova in three close sets, despite being up a break two times in the final set.
Wozniacki was seeded 17th at the Australian Open. She reached the third round, after defeating Arina Rodionova and Donna Vekic, but was defeated by 9th seed and in-form Johanna Konta in straight sets.
After the Australian Open, Wozniacki played at the Qatar Total Open sliding past Kiki Bertens and Agnieszka Radwanska in the first two rounds in straight sets. She then savied two set points in the first seat to beat Lauren Davis, before dispatching Monica Puig to reach the final. There she fell to the in-form Karolína Plíšková. From there she played at the Dubai Tennis Championships, also making the final there by beating Daria Kasatkina, Viktorija Golubic, Kateryna Bondarenko, Catherine Bellis, and Anastasija Sevastova respectively before coming up short against Elina Svitolina in straight sets in the final. Despite runner up finishes, Wozniacki rose back up to No. 14.
At the BNP Paribas Open, Wozniacki beat Magda Linette, Kateřina Siniaková, and Madison Keys, without the loss of a set, to advance to the quarterfinals where she lost to Kristina Mladenovic. At the Miami Open, Wozniacki beat Varvara Lepchenko and Sorana Cîrstea in straight sets before advancing to the quarterfinals after a retirement from Garbiñe Muguruza. In the quarterfinals, she beat Lucie Šafářová in straight sets and in the semifinals, avenged her Doha loss to Karolína Plíšková by beating her in three sets to advance to her first ever final in Miami and her first Mandatory final since 2013. She lost in straight sets to Johanna Konta.
Wozniacki began her clay court season at the Volvo Car Open. She made it to the quarterfinals with straight set wins over Annika Beck and Anastasia Rodionova. There she lost to Jeļena Ostapenko in straight sets. She next played at the Prague Open and after beating Misaki Doi in the first round in straight sets, she lost to Ostapenko again in three sets despite having match point. Wozniacki next played at the Madrid Open. In the first round, she beat Monica Niculescu in three sets before losing to Carla Suárez Navarro in three sets. In Strasbourg, Wozniacki retired from her first match against Shelby Rogers after losing the first set in a tiebreak. Wozniacki then played at French Open as the 11th seed. She beat Jaimee Fourlis in the first round in three sets, before beating Françoise Abanda, without the loss of a game. In the third round she beat CiCi Bellis in three sets after being down a break in the third and then went on to beat former champion Svetlana Kuznetsova in three sets to advance to the quarterfinals for the first time since 2010. She lost to eventual champion Jeļena Ostapenko for the third time in three sets.
Wozniacki began her grass season at the Aegon International with straight set wins over Naomi Osaka and Elena Vesnina. In the quarterfinals, she came from a set and a double break down to beat Simona Halep and proceeded to beat Heather Watson in three sets to advance to her fourth final of the year where she lost to Karolína Plíšková in straight sets. She then played at Wimbledon as the fifth seed. She beat Timea Babos in three sets, recovering from a break down and grass court specialist Tsvetana Pironkova in straight sets. She then beat Anett Kontaveit in a come from behind three set win which saw Kontaveit fail to serve for the match twice to advance to the fourth round for the sixth time. She lost to Coco Vandeweghe in straight sets.
After Wimbledon Caroline competed in the Swedish Open there she made the her fifth final of the year passing through Pauline Parmentier, Viktorija Golubic, Kateryna Kozlova, and Elise Mertens before falling to Katerina Siniakova in the final. Wozniacki began her hard court season in Rogers Cup in Toronto. Here she won her first ever match in Toronto defeating Ekaterina Alexandrova later in the Quarterfinals she defeated the current world No. 1 for the first time, overcoming Karolina Plíšková in three sets. Wozniacki eventually made her 6th final of 2017 yet again falling at this stage, this time to Elina Svitolina. This tipped Wozniacki back into the top 5. She then competed in the Cincinnati Open defeating Elena Vesnina and Ashleigh Barty before falling in the quarterfinals to world No. 1 Karolina Plíšková.
Wozniacki and her good friend Serena Williams have met 11 times with Williams leading the head to head 10–1. Williams leads 2–0 in Grand Slams, 8–1 on hard courts, and 1–0 on both clay and grass. Both held the no.1 ranking from early November 2009 to late January 2012. They are currently the Top 2 active players to hold the no.1 ranking for the most weeks.
They first met at the 2009 Medibank International Sydney with Williams winning in three tight sets saving match points. Wozniacki's only win over Williams came at the 2012 Sony Ericsson Open where she won in straight sets. In 2014 the rivalry reached its peak with the pair meeting four times and Williams winning all of them. Three of their four meetings went to three sets with Williams coming from a set down in each to win. At the Rogers Cup Wozniacki led by a set and a break before Williams came back to win it. They would meet a week later at the Western & Southern Open where Williams again came from a set down to win. They faced off against each other in the final at the US Open where Williams won in straight sets to claim her 18th Grand Slam title. Their most recent meeting at the WTA Finals was an epic with Wozniacki winning the first set before Williams came back to win the second set. At 4–4 Wozniacki broke Williams to serve for the match and Williams broke back. At 6–5 Wozniacki saved match point with an incredible volley and held serve to take the set to a tiebreak. In the tiebreak Wozniacki was up 4–1 before Williams came back and eventually prevailed.
Despite being rivals, the two maintain a strong friendship off court. Wozniacki visited Williams during her recovery from injury in 2011. In 2014 after they both lost early at the French Open they vacationed together in Miami. They attended a Mariah Carey concert the night before their semifinal match at the WTA Finals. Williams was present during Wozniacki's run at the New York City Marathon. They also went on a mini tour around New York City.
Wozniacki and Agnieszka Radwańska have met 16 times with Wozniacki leading the head to head 11–6. Wozniacki leads 9–6 on hard courts and 2–0 on clay.
They first met at the 2007 Nordea Nordic Light Open with Radwańska winning in straight sets. After that win, Wozniacki would win the next 5 matches before having the streak snapped at the 2012 Apia International Sydney where she lost in three sets. Radwańska would then win the next 2 matches before that streak was snapped at the 2014 Western & Southern Open where she would lose in straight sets. Their most recent meeting was at the 2017 Qatar Total Open where Wozniacki won in straight sets.
Wozniacki and Maria Sharapova have met 10 times with Sharapova leading the head to head 6–4. Wozniacki leads 2–0 in Grand Slams with both coming at the US Open in 2010 and 2014. Wozniacki leads 4–3 on hard courts, while Sharapova leads 3–0 on clay.
The pair first met at the 2008 Qatar Total Open where Sharapova won in straight sets and then again at the 2008 Rome Masters. Wozniacki then won the next two meetings to tie the head-to-head. Sharapova then won the next three meetings including their only meeting in a final at the 2013 BNP Paribas Open. Wozniacki snapped the losing streak by beating Sharapova in three sets at the 2014 US Open and would go on to the reach the final. They met again at the 2014 WTA Finals where Wozniacki won in three sets in a marathon match that lasted over three hours. Their most recent meeting was at the 2015 Mutua Madrid Open where Sharapova won in three sets.
Wozniacki's father, Piotr, has been her primary coach since she was 14. Throughout the years, she was coached by Sven Groeneveld through the Adidas Player Development Program. She was briefly coached by Ricardo Sanchez and Thomas Johansson. In October 2013, she hired Thomas Högstedt, but parted ways in January 2014. In the same month, she hired Michael Mortensen, but cut ties with him in March 2014. Since then, Wozniacki has decided to be coached again by her father Piotr for the rest of her career.
Wozniacki's best friend is her fellow Danish tennis player Malou Ejdesgaard, who has been her doubles partner in five tournaments. Wozniacki is also close friends with Serena Williams, Agnieszka Radwańska and Angelique Kerber. She speaks Danish, English and Polish fluently.
When asked in 2008 by Teen Vogue magazine what sports beside tennis she liked to play, Wozniacki said "I like handball, soccer, swimming, playing the piano, and all kinds of different things." A fan of English Premier League team Liverpool, she wore a Liverpool shirt signed by footballer Steven Gerrard on court in the 2011 Qatar Ladies Open.
Wozniacki was in a relationship with Northern Irish professional golfer Rory McIlroy from 2011 until 2014. She announced their engagement on her Twitter page on 1 January 2014. On 21 May 2014, it was announced that McIlroy had ended the engagement: "The problem is mine. The wedding invitations issued at the weekend made me realise that I wasn't ready for all that marriage entails. I wish Caroline all the happiness she deserves and thank her for the great times we've had."
On February 14, 2017, on Valentine's Day, Wozniacki revealed on her social media account that she was in a relationship with former NBA champion and current San Antonio Spurs player David Lee, later being confirmed by her family.
On 2 November 2014, Wozniacki made her marathon debut, completing the New York City Marathon in a time of 3:26:33. This time was good enough to qualify for the 2016 Boston Marathon but Wozniacki said she will not run another marathon for a few years.
Wozniacki appeared in the 2015 Sports Illustrated Swimsuit Issue, following other number one-ranked singles tennis stars: Steffi Graf (1997), Serena Williams (2004), Venus Williams (2005), Maria Sharapova (2006), Ana Ivanovic (2010) and Rafael Nadal (2012) who have appeared in the issue.