Born in Manhattan to a social worker mother and lawyer father, Amanda Peet made her screen debut in a commercial for skittles. Her first film was 1995's Animal Room, starring Neil Patrick Harris. In 1996 came roles in She's the One, alongside Jennifer Anniston and Cameron Diaz, and One Fine Day, starring George Clooney and Michelle Pfeiffer. The next year brought guest starring roles on Spin City and Seinfeld.

Peet continued to build up a solid film resume before landing her first regular television role in 1999, playing Jacqueline "Jack" Barrett on Jack & Jill. In 2000, she appeared in the film The Whole Nine Yards, receiving the "Choice Film Liar" Teen Choice Award for her role as Jill St. Claire. Peet continued to work steadily in films through the 2000s, appearing in movies such as Something's Gotta Give opposite Diane Keaton and Jack Nicholson, A Lot Like Love opposite Ashton Kutcher, and Syriana opposite George Clooney and Matt Damon. In 2006, she returned to television with a regular role on Aaron Sorkin's series Studio 60 on the Sunset Strip. That year, she also made her Broadway debut in Neil Simon's play Barefoot in the Park.

Since the end of Studio 60 on the Sunset Strip, Peet has appeared in movies including The X Files: I Want to Believe and The Way Way Back. She also had a recurring role in The Good Wife from 2012 to 2013. Most recently, she's starred in the acclaimed HBO series Togetherness.