UNC spokesman Steve Kirschner said Williams, 65, got dizzy but is doing OK. The incident occurred during the first media timeout of the second half.
Kirschner gave another update about 20 minutes later and said that Williams got up from his chair too fast, triggering a bout of vertigo. Williams received medication and was expected to remain in the locker room for the remainder of the game.
After play was halted for the timeout, Williams began arguing with an official before turning toward North Carolina's bench area, where he lost his balance and attempted to brace himself by holding onto a folding chair. He was immediately tended to by multiple Tar Heels players and assistant coaches.
Assistant coach Steve Robinson assumed coaching duties on the sideline.
Williams had bouts with vertigo in the past and felt dizzy when standing up quickly.
The Tar Heels are concluding a three-game road trip. Their last home game was Jan. 30 against Boston College.
The Associated Press contributed to this report.