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.