At the age of 16, Lynskey landed her first acting role in Peter Jackson's critically acclaimed film "Heavenly Creatures", co-starring with Kate Winslet. She played Pauline Parker, a teenage girl involved in a matricide. This role launched her international career and brought her immediate recognition.

Following the success of "Heavenly Creatures", Lynskey briefly attended Victoria University of Wellington, studying arts, including English literature. She did not complete the course as acting opportunities continued to arise.

Melanie starred in "The Eternal" directed by Michael Almereyda and alongside Christopher Lambert. She also appeared in "Ever After: A Cinderella Story", portraying Jacqueline, one of Cinderella's stepsisters. This role showcased her ability to play diverse characters, ranging from dramatic to comedic.

Melanie appeared in "Detroit Rock City", a comedy about four teenagers on a quest to see the rock band Kiss in concert in Detroit in 1978. She played Beth, one of the main character's girlfriends.

Melanie portrayed Gloria in "Coyote Ugly", a film about a young songwriter who moves to New York City to pursue her dreams and finds work at a trendy bar.

Lynskey appeared in the popular romantic comedy "Sweet Home Alabama", further solidifying her presence in Hollywood. Her role as Lurlynn showcased her ability to blend into ensemble casts and deliver memorable supporting performances.