It follows a troubled Brooklyn high school student, who decides to channel her aggression by training to become a boxer, despite the disapproval of her father and prospective trainers, as well as the competitors in the male-dominated sport.

Kusama wrote the screenplay for Girlfight after learning to box, wanting to make a film about the sport with a female protagonist.

Girlfight premiered at the Sundance Film Festival on January 22, 2000, where it tied with You Can Count on Me for the Grand Jury Prize, and Kusama won the Best Director Award.

Her frustration stems from her unhappy home life; she lives in a public housing estate with her brother Tiny and their abusive father, Sandro.

After writing the script, she struggled to persuade production companies to finance the film; numerous producers suggested that Kusama cast a white woman in the lead role rather than a Latina and felt that having a female protagonist was "unappealing [and] unbelievable".

Maggie Renzi, Sarah Green and Martha Griffin eventually agreed to produce the film, and found a financier in 1999 to provide the $1 million budget.

[2] Michelle Rodriguez, who had worked as a film extra but had never auditioned for a speaking role before, attended an open casting call for the lead.

[1] Since Rodriguez was not a boxer, she trained at Gleason's Gym five to six days a week for four months in preparation for filming,[4] as did Santiago Douglas, who was cast as Adrian.

The website's critical consensus states: "Michelle Rodriguez gives a compelling performance, despite lack of a boxing background; Karyn Kusama packs a punch with this directorial debut.

[19] David Denby of The New Yorker called her "a powerhouse star who could go a long way",[20] while Variety critic Emanuel Levy described her as "a natural performer who dominates every scene".

"[22] The Washington Post's Desson Howe felt that Rodriguez's performance was the most memorable aspect of the film, and that she "becomes more appealing, formidable and beautiful by the scene".

The Los Angeles Times's Kenneth Turan commended her "craft, empathy and respect" and compared her to the character of Diana, writing that Kusama "is her protagonist's double in terms of drive, commitment and ability".

[24] Lisa Schwarzbaum of Entertainment Weekly felt that, although the plot was clichéd and unrealistic at times, Kusama's direction showed "a clear, personal filmmaking style ... and a respect for her characters' weaknesses as well as their moments of athletic beauty".

[25] James Berardinelli gave the film three and a half stars out of four, calling it "a well crafted and emotionally satisfying debut" and applauding Kusama's "single-minded determination and a passion for the project".

[27] On the other hand, the San Francisco Chronicle's Edward Guthmann opined that Kusama "ultimately undercuts her theme of female self-reliance by having Diana fall for Adrian" and criticized the plot for "tak[ing] too much time justifying a woman's right to be in the ring – instead of celebrating her achievement".