Dulko retired from professional tennis on 18 November 2012, aged 27.
Gisela was born and raised in Tigre, Buenos Aires Province. Her brother Alejandro, who is seven years her senior, is her coach. Gisela was born to Ana and now deceased Estanislao, who was of Hungarian descent. At the age of twelve, she moved from Argentina to Miami, Florida, in order to pursue a professional tennis career.
Dulko is married to fellow Argentine, Fernando Gago, who is a football player currently playing for Boca Juniors. The couple had their first child, Mateo on 9 June 2013.
As a Junior, she won three of the four Grand Slam events in doubles, including the 2000 US Open with María Emilia Salerni, the 2002 Australian Open with Angelique Widjaja, and the 2001 Wimbledon Championships with Ashley Harkleroad. As a professional, she has won sixteen doubles championships.
In singles, Dulko has had a less successful career, although she has been consistently ranked in the Top 50 over the last few years. On 29 April 2007, Dulko finally won her first WTA Tour title by defeating Sorana Cîrstea of Romania in the final of the Tier III event in Budapest. On 25 August 2007, Dulko won her second WTA Tour title at the Forest Hills Tier IV event defeating Virginie Razzano. On 4 May 2008, Dulko won her third WTA Tour title at the Grand Prix SAR La Princesse Lalla Meryem Tier IV event defeating Anabel Medina Garrigues.
In January, she obtained an invite from Hong Kong Tennis Patrons' Association to play JB Group Classic 2009 with two Americans Coco Vandeweghe and Venus Williams, and then she started the year with a Quarterfinals appearance at the 2009 Moorilla Hobart International losing to Iveta Benešová. At the 2009 Australian Open she lost to eventual champion Serena Williams in the second round. In the 2009 Fed Cup first round, she gave her team their only wins when she defeated Americans Melanie Oudin and Jill Craybas. In the 2009 Copa Sony Ericsson Colsanitas she reached her first final of the year, but then lost to María José Martínez Sánchez. She then made good performances by reaching the quarterfinals of the 2009 Monterrey Open and 2009 Porsche Tennis Grand Prix, and the Third Round of Mandatory Events in Indian Wells and Miami. She however lost in the second rounds of the 2009 Internazionali BNL d'Italia and 2009 Internationaux de Strasbourg and a first round exits in 2009 Mutua Madrileña Madrid Open and the 2009 Aegon International.
She reached the third round in the next two Grand Slams, losing to Dominika Cibulková at the 2009 French Open, and to Nadia Petrova at the 2009 Wimbledon Championships. At the 2009 Wimbledon Championships, Dulko upset No. 24 seeded Maria Sharapova in three sets in the second round.
At the 2009 Swedish Open, she lost again to María José Martínez Sánchez, this time in the semifinals. She then made first round exits in the 2009 Internazionali Femminili di Palermo, the 2009 LA Women's Tennis Championships, the 2009 Pilot Pen Tennis and failed to qualify for the 2009 Rogers Cup. At the 2009 US Open, she made it to the Round of 16 before falling to Kateryna Bondarenko 6–0, 6–0 in just 47 minutes. Her last tournament of the year was at the 2009 Toray Pan Pacific Open where she reached the second round before losing to Iveta Benešová in three sets.
She obtained an invite from the Hong Kong Tennis Patrons' Association once again to play Hong Kong Tennis Classic and won Silver Group Championships with two Americans Venus Williams and Michael Chang, and then she started the year at the 2010 Moorilla Hobart International where she reached the quarterfinals losing to Anabel Medina Garrigues. At the 2010 Australian Open, she upset Ana Ivanovic in the second round before losing to 9th seed Vera Zvonareva. She then played in 2010 Copa BBVA-Colsanitas as the top seed, and made it to the semifinals before being upset by Angelique Kerber. There, she won the doubles title with Edina Gallovits. She then played in the 2010 Abierto Mexicano Telcel as the 3rd seed but lost to 5th seeded Spaniard Carla Suárez Navarro in the semifinals.
Seeded 31st at the 2010 BNP Paribas Open in Indian Wells, she received a bye in the first round. In the second round she gained the biggest victory of her career by defeating former world No.1 Justine Henin in just over 2 hours. In the third round, she lost to No.5 seed Agnieszka Radwańska.
Unseeded at the 2010 Sony Ericsson Open, Dulko reached the third round by defeating Olga Govortsova and No.21 seed Alona Bondarenko. She then lost to Marion Bartoli in the fourth round. In doubles, Dulko teamed together with good friend Flavia Pennetta. Despite playing in only their third event together of the season, they won their first WTA Premier doubles title, beating Nadia Petrova and Samantha Stosur in three sets.
Dulko and Pennetta next teamed together in the 2010 Porsche Tennis Grand Prix in Stuttgart, and won the tournament, extending their winning streak to ten matches. Their winning streak was extended to fifteen matches by winning the 2010 Internazionali BNL d'Italia in Rome. They extended their streak to 19 matches before losing in the final of the 2010 Mutua Madrileña Madrid Open to Serena and Venus Williams, the Australian Open and eventual French Open champions.
Dulko caused the first upset of the 2010 French Open with a first round victory over No. 10 Victoria Azarenka. Dulko was then defeated by Chanelle Scheepers in the second round. Dulko was then upset in the first round of her Wimbledon campaign by Monica Niculescu. She and Pennetta reached the semifinals of the doubles event there before losing.
Dulko then played at the 2010 Collector Swedish Open in Båstad where she was seeded fourth. Although Dulko overcame her doubles partner Flavia Pennetta in the semifinals, she fell in the final to French No. 2 Aravane Rezaï in three sets. Dulko and Pennetta went on to defend their doubles title there by defeating the Czech pair of Renata Voráčová and Barbora Záhlavová-Strýcová, earning their fourth team title of the season and seventh overall.
Dulko and Pennetta won a marathon doubles final at the 2010 Rogers Cup in Montreal, beating Květa Peschke and Katarina Srebotnik, for their fifth event of the season. Their very next event together was the 2010 U.S. Open, in which they were the top seeds for the event.
In singles, Dulko made it to the third round before losing to twentieth seed Anastasia Pavlyuchenkova. In doubles, Dulko and Pennetta lost in the quarterfinals to Vania King and Yaroslava Shvedova, the eventual champions.
At the 2010 China Open in Beijing, Dulko made it to the second round before falling to Maria Kirilenko. She would lose in the first round of her remaining tournaments. In doubles, Dulko and Pennetta fell in the final in Beijing to Olga Govortsova and Chan Yung-Jan, and then won their sixth combined event at the 2010 Kremlin Cup in Moscow. Because of their outstanding doubles efforts, Dulko and Pennetta were invited to the 2010 WTA Tour Championships in Doha, Qatar, where they are the top seeds. They ended up defeating Peschke and Srebotnik in the final to win the 2010 WTA Tour Championships
On 1 November 2010, Dulko became the world no. 1 ranked doubles player.
Dulko teamed with Pennetta to win their first Grand Slam event title by winning the 2011 Australian Open. Top seeds Dulko and Pennetta defeated Victoria Azarenka and Maria Kirilenko, 2–6, 7–5, 6–1, in the final.
Gisela made her first singles final of the year at the 2011 Abierto Mexicano Telcel where she was fourth seed. There she defeated Arantxa Parra Santonja to win her fourth career singles title.
Gisela struggled in her next few tournaments, losing in the first rounds of Miami, Madrid, and Rome, and only reaching the second round at 2011 BNP Paribas Open.
Gisela found her good form again at the 2011 French Open, advancing to the fourth round by defeating 2010 French Open finalist Samantha Stosur in three sets. However, she was forced to retire due to injury to her left leg early in the second set of her match against Marion Bartoli.2010 — WTA Award for Doubles Team of the Year (with Flavia Pennetta)
2010 — ITF Doubles World Champion (with Flavia Pennetta)