She represented the United States as member of United States U-17, U-18, and U-20 national soccer teams. On February 13, 2013, she made her debut in the senior team playing a friendly match against Scotland national women's football team.
Born in New Hyde Park, New York, to Vincent and Rhonda Dunn, Crystal was raised with her brother Henry in Rockville Centre, New York where she attended South Side High School. At South Side, she was a four-year starter as forward and midfielder and team captain in 2008 and 2009. She lost only two matches in three seasons at South Side and helped lead her team to New York state championships in 2006, 2007 and 2009. In the 2009 state championship match, she scored four goals and had a hat trick in the first 20 minutes of the match.
Dunn scored 46 goals and had 35 assists in three high school seasons, missing the 2008 season due to national team commitments. She was a highly decorated high school player earning Parade All-American and New York Player of the Year. She also earned First-team All-State and All-Long Island honors in 2006, 2007 and 2009. As a freshman, sophomore and senior, she was an All-New York First Team and All-Long Island team selcection. In 2009, she was named 2009 NSCAA, ESPNRise and Parade high school All-America and was the New York Gatorade High School Player of the Year. The teams she played on in 2007 and 2009 went undefeated and were ranked number one in the nation by the NSCAA.
As a senior, she was named Newsday Long Island Player of the Year, Nassau County Class A Player of the Year, New York Sportswriters Class A Player of the Year, BigAppleSoccer.com youth Player of the Year and was the winner of the Mike Clark Award for the best all-around athlete in Nassau County.
In addition to her high school experience, Dunn played with the club teams, Albertson Fury, the RVC Tornadoes, and the RVC Power (with whom she won a state title).
Dunn attended the University of North Carolina, Chapel Hill and majored in sociology. As a freshman in 2010, Dunn started 23 matches and played the entire match 18 times for a total of 1,929 minutes. She was the team's leading player in points with 26 including nine goals and eight assists. She scored four goals during the NCAA Division I Women's Soccer Championship including a match-winner against Jackson State, a goal against Notre Dame, and two goals in a 3–1 win over James Madison in the second round of the tournament. Her accolades during her freshman year season included: Soccer America Freshman of the Year, 2010 NSCAA first-team All-America honoree, Second-team Soccer America MVP selection, First-team All-ACC. She was the first freshman to ever win the ACC Defensive Player of the Year award and was a semifinalist for the 2010 Missouri Athletic Club Hermann Trophy.
As a sophomore in 2011, Dunn started 19 matches missing only one while she was training with the United States under-20 women's national soccer team. She scored three goals and made six assists during the season. She was named third-team All-America and first-team All-Southeast Region by the NSCAA. She was also named to the first-team All-ACC and was named to the Top Drawer Soccer National Team of the Week three times.
During her junior season in 2012, Dunn missed the non-conference phase of the 2012 college season while playing for the United States under-20 women's national soccer team at the 2012 FIFA U-20 Women's World Cup in Japan. Following her return, she helped lead the Tar Heels to win the NCAA Women's Soccer Championship. During the tournament's quarter-final, Dunn scored both goals in a 2–1 win against top-seed team BYU, including a match-winning "golden" goal within four minutes of end of second overtime. She also saved her team from trailing BYU when she headed the ball away from the Tar Heels' goal-line in the first overtime. Dunn was named the 2013 Hermann Trophy winner as well as the ACC Athlete of the Year and ACC Defender of the Year. Dunn was an All-ACC selection for the third straight year and an ESPY Awards finalist. She also was awarded the 2012 Honda Award for Soccer.
During her senior-year season in 2013, Dunn scored the first hat-trick of her collegiate career ending a 2-match losing streak for the Tar Heels after defeating the Miami Hurricanes 4–0. She led the team with 14 goals and 34 points, including six match-winning goals. Dunn was named ACC Offensive Player of the Year, NSCAA All-American and First-team All-ACC for the fourth consecutive year. She was a Hermann Trophy finalist and a nominee to Honda Award.
In January 2014, Washington Spirit selected Dunn with the first overall pick in the 2014 College Draft for the 2014 season of the National Women's Soccer League. She made 19 starts for the Spirit in her 22 appearances for the club during the 2014 season. The team finished fourth during the regular season with a 10–9–5 record securing a place in the playoffs. During the semifinal, the Spirit were defeated by regular season champions Seattle Reign FC 2–1 on August 31 in Seattle.
Dunn returned to the Spirit for the 2015 season. On April 26, 2015, she scored two goals while playing in the defender position in a match against Sky Blue FC helping the Spirit win 3–1. She was subsequently named NWSL Player of the Week for week 2 of the season.
On August 1, 2015, Dunn scored a franchise first hat trick, scoring three goals in the first half, in the Spirit's victory over the visiting Houston Dash. She finished the month with six goals, earning her the league Player of the Month award.
Dunn finished the regular season with a league-leading 15 goals, giving her the 2015 NWSL Golden Boot and the league Most Valuable Player award. She became the youngest player to win both awards at age 23 and broke the league record with her 0.77 goals-per-game average.
Dunn returned for her third season in 2016, scoring four goals and notching a career-high five assists. Two of her four goals were the two Spirit goals scored in the team's first ever appearance in the NWSL Championship.
On January 3, 2017, Dunn joined FA WSL 1 club Chelsea. In June 2017, Chelsea won the FA WSL Spring Series.
Dunn has competed on behalf of the United States in various national youth teams from 2008 through 2012, including at the 2008 FIFA U-17 Women's World Cup. In the U.S. Under-20 teams, she is one of leaders in number of caps played. She was in the 2010 FIFA U-20 Women's World Cup in Germany and was a member of the team that won the 2012 FIFA U-20 Women's World Cup in Japan.
On January 22, 2013, Dunn received her first call-up to the senior team's training camp, by the newly appointed coach Tom Sermanni. Dunn made her debut for the team, on February 13, against Scotland national women's football team in a friendly match; and was placed on the roster for 2013 Algarve Cup.
Dunn made her first Algarve Cup appearance for the senior team during the team's first match in the tournament on March 6, 2013 against Iceland. She started the match at left back and played for the full 90 minutes. The United States defeated Iceland 3–0. Dunn earned her third cap with the senior team during the final match of the tournament against Germany. The United States clinched the tournament championship after defeating Germany 2–0.
In October 2014, she was dropped from the national team roster ahead of the 2014 CONCACAF Women's Championship, which served as the qualifying tournament for the 2015 FIFA Women's World Cup. Dunn returned from injury in December 2014 and traveled with the team to Brazil, but did not play.
Dunn was named to the roster for February 2015 friendlies against France and England, and made a substitute appearance against England. February 2015, Dunn was named to the 2015 Algarve Cup roster, but did not play a single minute. Dunn was named to the preliminary for the 2015 Women's World Cup, but did not make the final squad of 23.
In September 2015, Dunn was added to the roster for the national team's Women's World Cup victory tour prior to September 17 match against Haiti, becoming the first player not on the World Cup roster to join the tour. Dunn made her first start of 2015 against Haiti and earned her first cap since the England friendly. She recorded her first career national team assists, both on Carli Lloyd's goals, and scored her first national team goal in the final moments of the match.
Dunn played in the national team's opening game of the CONCACAF Women's Olympic Qualifying Championship. She scored her fifth international goal in the 5–0 victory over Costa Rica.
In the third group match vs Puerto Rico, Dunn tied for the most goals scored by a U.S. player during a match, netting 5 goals and an assist during the match.
University of North CarolinaNCAA Women's Soccer Championship: 2012
ChelseaFA WSL Spring Series: 2017
FIFA U-20 Women's World Cup: 2012
Algarve Cup: 2015
SheBelieves Cup: 2016
Hermann Trophy: 2012
Atlantic Coast Conference Player of the Year: 2012
ACC Defensive Player of the Year: 2010, 2012
Soccer America Player of the Year Award: 2012
Top Drawer Soccer Player of the Year Award: 2012
Honda Award for Soccer: 2012
NWSL Player of the Week: 2015 (Weeks 3, 8, 11, 16, 18)
NWSL Player of the Month: August 2015
NWSL Most Valuable Player: 2015
NWSL Best XI: 2015
NWSL Golden Boot: 2015 (15 goals)
CONCACAF Women's Olympic Qualifying Tournament Golden Boot: 2016 (6 goals)
Dunn has been featured in Self Magazine. In 2016, she starred with teammates Hope Solo and Megan Rapinoe in a docu-series called Keeping Score broadcast by Fullscreen. The episodes follow the athletes as they prepare for the 2016 Rio Olympics and address issues such as equal pay and racism.