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 selection. 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.

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 in the first 20 minutes of the match.

Dunn attended the University of North Carolina, Chapel Hill and majored in sociology. As a freshman in 2010, Dunn started 23 matches for a total of 1,929 minutes, playing the full 90 minutes 18 times. 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 first year season included Soccer America Freshman of the Year, 2010 NSCAA first-team All-America honoree, Second-team Soccer America MVP selection, and First-team All-ACC. She was the first freshman ever to win the ACC Defensive Player of the Year award and was a semi-finalist for the 2010 Missouri Athletic Club Hermann Trophy.

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 the 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.

As a sophomore in 2011, Dunn started in 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 the end of the second overtime. She also saved her team from losing to 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 two-match losing streak for the Tar Heels by 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.

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 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 semi-final, the Spirit were defeated by regular season champions Seattle Reign FC 2–1 on August 31 in Seattle.

In October 2014, Dunn 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 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 the franchise’s first hat trick, scoring three goals in the first half of 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 won 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. She has said that being left off the national team for the 2015 World Cup gave her extra motivation in the league.

In September 2015, Dunn was added to the roster for the national team’s Women’s World Cup victory tour prior to the September 17 match against Haiti, becoming the first player not on the World Cup roster to join the tour. She 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 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, which was won on penalties by the Western New York Flash after a 2-2 draw.

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.

On January 3, 2017, Dunn joined FA WSL 1 club Chelsea. On March 19, she scored her first goal just 12 minutes into her first competitive appearance for the club, in a 7–0 FA Cup win over Doncaster.

After a year in England, it was planned that Dunn would return to North America with the deal of a trade with Washington Spirit for two of North Carolina’s players at the time, Taylor Smith and Ashley Hatch. The Spirit retained the League rights after Chelsea signed Dunn back in January 2017. This move was confirmed by Chelsea on February 25, 2018.

She made her first appearance for the North Carolina Courage in a 1–0 win over Portland Thorns FC, in the opening game of the 2018 NWSL season. Dunn was named Player of the Week twice in the 2018 NWSL season, for weeks 8 and 13. She was named Player of the Month for the month of June. Dunn appeared in 22 regular season games for the Courage, scoring eight goals, helping North Carolina win the NWSL Shield. The Courage broke the record for most goals scored in a season. Dunn was named to the 2018 NWSL Best XI.

Dunn married Pierre Soubrier in December 2018. They met when she was playing for the NWSL’s Washington Spirit, where he was working as an athletic trainer. Soubrier’s presence in Portland, where he is head trainer for the Portland Thorns, contributed to Dunn’s desire to get traded to Portland.

On October 22, 2020, Crystal Dunn was traded to OL Reign in exchange for Casey Murphy and $140,000 in allocation money. Later that day, she was traded to the Portland Thorns in exchange for an international roster slot, a 2022 first round draft pick, and $250,000 in allocation money.

On February 7, 2020, Dunn played her 100th match for the United States in a 4–0 win against Mexico.