Williams is in jail Sunday. He had come to Portland to perform in Nick Cannon's "Wild 'N Out" comedy improv show Friday night.
Port of Portland police say the town car driver had swelling and cuts on his face. The 47-year-old Williams left in another vehicle and was arrested Saturday.
Williams has been charged with assault in the fourth degree. An arraignment is scheduled for Monday. He also was arrested for an out-of-state warrant.