Leigh started acting at an early age and debuted in the film world at age 15 in 1997's Kickboxing Academy. In this movie, her real life brother plays her love interest. In the movie, there are several scenes in which the two siblings kiss passionately. In 2001, Leigh had the lead role in the film Not Another Teen Movie as Janey Briggs. She also appeared in Marilyn Manson's music video "Tainted Love", a song which appeared in the film. She was ranked #65 on the Maxim Hot 100 Women of 2002.

In 2002, Leigh was cast in two short-lived TV series: Girls Club, in which she played lawyer Sarah Mickle, and That '80s Show, in which she played punk rocker June Tuesday. She then became a series regular on the ABC legal drama The Practice, but was let go at the end of the season due to budget cuts. Following that, she joined the cast of Reunion in September, 2005. In ABC's Grey's Anatomy, Leigh first appeared as a woman in Joe's bar who tried to pick up Derek Shepherd. In the third season