Lacey Chabert was born in Purvis, Mississippi to Julie, a homemaker, and Tony Chabert, a French-speaking Cajun from Louisiana who worked as a maintenance operations representative for an oil company. Lacey has a brother, T.J., and two sisters, Wendy and Crissy. Chabert lives in Southern California, where she moved with her family in 1994 when she began work on Party of Five. In 1998, she stated, "Yes, I am a Christian. Jesus is the center of my life and I give God the glory for everything, for all my success" and has expressed displeasure with the fact that Black Christmas was released directly on Christmas Day.

Since 1998, Chabert has been the voice of Eliza Thornberry in the animated series "The Wild Thornberrys"; she also voiced Eliza in two Wild Thornberrys movies, "The Wild Thornberrys Movie" (2002) and "Rugrats Go Wild!" (2003). Lacey also provided the voice of Meg Griffin for the first production season of the animated sitcom "Family Guy" (1999), after which Mila Kunis took over the role. Actress also played the title role in "The Brooke Ellison Story", a made-for-TV movie produced by Christopher Reeve, based upon a real-life quadriplegic woman who overcame many obstacles to graduate from Harvard. She also starred in "Daddy Day Care" (2003), "Mean Girls" (2004) and the made for TV movie "Hello Sister, Goodbye Life" (2006) on ABC Family. Chabert appeared in a 2006 remake of Black Christmas. Chabert also performed the voice of Princess Elise from the game Sonic the Hedgehog for the PS3 and Xbox 360. She will also provide Gwen Stacy's voice in the upcoming animated series The Spectacular Spider-Man, set to debut in 2008.

In 2007, Lacey starred in the FOX comedy pilot The Hot Years, which revolved around the lives of four female friends who live together. The pilot was not ordered to series by FOX. Chabert was featured as cover girl of the January 2007 issue of Maxim.