Amanda Peet was born and raised in New York City, the daughter of Penny (Levy),a social worker, and Charles Peet, a lawyer, who had an older sister. Her father was of mostly English and German ancestry, while her mother was from a Jewish family with roots in Germany, Russia, and Hungary. Peet's great-grandfathers were notable figures, including politician Samuel Levy and showbiz impresario S.L. Rothafel.
Peet made an unconventional stage debut at the age of three, when she jumped onto the stage during a play. Despite this early start, she did not pursue acting as a career until later, instead studying history at Columbia University. A drama professor at the university convinced her to audition for acting teacher Uta Hagen, with whom she later studied for four years. During this time, she participated in the off-Broadway revival of Clifford Odets' "Awake and Sing."
To support herself during the audition phase of her career, Peet worked as a waitress and received residual checks from a Skittles candy commercial. Her perseverance and hard work eventually paid off, and in 1995, she was cast in a guest-starring role on the hit series Law & Order.
Peet's feature film debut came in 1995 with the movie Animal Room. She continued to find steady work, but also appeared in a number of indie films that were never picked up for distribution. However, she did meet her boyfriend Brian Van Holt on the set of the indie movie Whipped.
Peet's breakthrough role came in 2000, when she played the ditzy hit-woman with the heart of gold in the hit comedy The Whole Nine Yards, opposite Bruce Willis. Her performance earned her a spot on People Magazine's list of the 50 Most Beautiful People in the World that same year.