First working as a model in Australia and Europe, she moved to Los Angeles where she studied acting in 1991. She studied with people like Arthur Mendoza from The Actors Circle Theatre in Los Angeles, as well as Tom Waits at the TomKat Repertory Group. She landed small roles in independent films such as Loser and One of Our Own. But in 1996, ready to pursue her acting studies in New York, she was persuaded to audition for USA Network. She beat out 200 other actresses for the starring role in the Canadian television action series Nikita (U.S. title: La Femme Nikita) playing the role of Nikita, codenamed Josephine, a martial arts trained covert agent. The show was based on Nikita, a Luc Besson movie of the same name.

The show was a successful spring board for Peta's career in fact she received two Gemini nominations for Best Performance By An Actress in a Continuing Leading Dramatic Role.

In 2003, Wilson appeared in the movie The League of Extraordinary Gentlemen with Sean