[6] Chastain attended Archbishop Mitty High School and helped lead the team to three consecutive Central Coast Section championships.

[6][7] Chastain attended University of California, Berkeley where she played as a forward for the Golden Bears and scored 15 goals as a freshman.

[6][8] Soon after, she underwent reconstructive anterior cruciate ligament (ACL) surgeries on both knees which caused her to miss the 1987 and 1988 seasons.

[6] After transferring to Santa Clara University ahead of the 1989 season, Chastain helped lead the Broncos to two consecutive Final Four NCAA College Cup appearances (for the first time ever) in 1989 and 1990.

[12] On June 1, 1988, she earned her first cap for the United States women's national soccer team during a match against Japan.

After coming in as a substitute forward, she scored five consecutive goals in the team's 12–0 win against Mexico during the 1991 CONCACAF Women's Championship.

Chastain was not called for the 1995 FIFA Women's World Cup in Sweden, in which the U.S. won the bronze medal.

This led to both praise and criticism from spectators and sports commentators, and the image of the celebration is considered a key symbol of women's athletics worldwide.

The team eventually won the league's championship title after defeating the Atlanta Beat in penalty kicks.

[30] On July 10, 1999, at the 1999 FIFA Women's World Cup Final at the Rose Bowl in Pasadena, California, after scoring the fifth kick in the penalty shootout to give the United States the championship, and the win over China in the final game, Chastain celebrated by spontaneously taking off her jersey and falling to her knees in a sports bra, her fists clenched, flexing her arms.

[31] Removing a jersey in celebration of a goal is so common in men's soccer that it has, at times, been cause for an automatic yellow card caution, according to the Laws of the Game.

[37][38] In the UEFA Women's Euro 2022 Final at Wembley, England striker Chloe Kelly celebrated her 110th-minute goal against Germany in the same way.

Like Chastain, Kelly's goal was a match and tournament winner – in Kelly's case, securing not only the Lionesses' first ever major trophy but the first England senior team major trophy (men's or women's) since the men's team won the 1966 World Cup as hosts.

Chastain acknowledged and congratulated Kelly, saying it put "a big smile on my face" and jokingly telling her to "enjoy the free rounds of pints and dinners for the rest of [her] life" from England fans.

[50] Chastain appeared as Candy in the season 6 premiere of Fresh Off the Boat, an episode which also included her World Cup–winning goal in 1999.

[57] Following the 1999 FIFA Women's World Cup, Chastain signed a number of endorsement deals, including Nike.

[59] In July 2016, she partnered with pharmaceutical company AbbVie Inc. to promote education and awareness about inflammatory bowel disease (IBD).

Her work with ABC/ESPN has included Major League Soccer matches and being part of a rotation of studio commentators for the 2011 FIFA Women's World Cup.