At the age of nine, Vanasse expressed her desire to sing or to act and she fulfilled that wish when she appeared in the teen show Club des 100 watts after winning a "lip sync" competition.

Producer Lorraine Richard and director Léa Pool spotted her there, and offered Vanasse her first big break in the role of Hanna in Set Me Free (Emporte-moi) (1999), a story of a teenager trying to find her identity in a tormented family environment.

[citation needed][2] Vanasse then played Lucie (the teenage love interest of Benoit Langlais's main character, Zac) in the controversial Québec TV series Deux frères (fr) (1999).

Her character became very prominent in 2000–2001, and the debate stirred by the violent realism led her to become, together with Langlais, a spokesperson for the government-funded TV program Parler, c'est grandir, a broadcast aimed at youngsters from unstable backgrounds.

Vanasse appeared in such Canadian productions as Sans Elle, Ma fille, mon ange, and the Canadian/American/British mini-series Killer Wave.

[7] In July 2013, Deadline Hollywood announced that Vanasse had joined the cast of ABC's Revenge as French businesswoman Margaux LeMarchal in the third season of the popular drama.