Williams first gained the attention of critics and audiences when he starred as Berger in Milos Forman's 1979 big-screen version of the seminal 1960s musical Hair, for which he received a Golden Globe nomination. Two years later, Williams earned his second Golden Globe nomination for his starring role in Sydney Lumet's Prince of the City.

Williams has since had starring roles in more than 40 feature films, most recently a role alongside Sandra Bullock in Ms. Congeniality 2 and Woody Allen's comedy Hollywood Ending. His other film credits include The Ritz, The Pursuit of D.B. Cooper, Once Upon a Time in America, Smooth Talk, for which he garnered an Independent Spirit Award nomination, Things To Do in Denver When You're Dead, Mulholland Falls, The Phantom, The Devil's Own, Deep Rising and The Deep End of the Ocean.