When Lefevre was working at a Montreal sushi restaurant as a teen, a regular customer heard about her acting aspirations and put her in touch with a casting director. This eventually led to a role on the Canadian sitcom Big Wolf on Campus.
Father's family is French, though Lefevre grew up speaking mostly English; she eventually moved to Los Angeles in 2004 due to a lack of English-speaking parts in Montreal.
Appeared on several episodes of David E. Kelley's Boston Legal, which led to a lead role in his 2008 U.S. adaptation of BBC hit Life on Mars.
Landed her biggest film role to date in Catherine Hardwicke's adaptation of Stephenie Meyer's Twilight, the first in a series of popular teen novels about vampires.