His first important role came in 1992 when he became a regular cast member on HBO's The Larry Sanders Show, where he played head writer Jerry.

One of Piven's early roles was Spike in Lucas (1986). Piven and Cusack once shared an apartment and have been friends since high school. He has appeared in a number of films with John Cusack, who is also from Evanston and is a fellow alumnus of the Piven Theatre Workshop (as are Cusack's sisters Joan and Ann). He spent a semester at the National Theater Institute at the Eugene O'Neill Theater Center in Waterford, Connecticut. He left Tisch during his senior year to pursue his acting career and is an alumnus of the Pi Kappa Alpha fraternity. He also attended Drake University in Des Moines, Iowa, where he departed after his sophomore year to attend New York University's Tisch School of the Arts. In Illinois, he trained at Piven Theatre Workshop, founded by his parents. As a teenager, he attended Harand Theater Camp in Elkhart Lake, Wisconsin, where he played Bernardo in West Side Story. He grew up in Evanston, Illinois, and graduated from Evanston Township High School. His elder sister is director Shira Piven, whom he has described as one of his first acting teachers his brother-in-law is director Adam McKay. His parents are Byrne Piven (1929–2002) and Joyce Hiller Piven (née Goldstein), both of whom were actors and drama teachers. Piven was born in Manhattan and raised in a Reconstructionist Jewish family of Ukrainian Jewish descent.

Tommy pixen