DuVall debuted in the 1990 film Deadly Dancer. After that he has also appeared in Pump Up the Volume (with Scott Paulin) and Scanner Cop (with Mark Rolston). He has also appeared in television series like "The Practice" (with Ryan Cutrona), "NYPD Blue" (with Lana Parrilla), "ER" (with Jose Zuniga), "Blind Justice" (with Marisol Nichols), and more recently "Supernatural". He also had a recurring role as Detective Darger in "The Guardian" (with Todd Jeffries and Evan Handler).
Stephen is the father of actress Clea DuVall.