Millsap checked in to the game with 5:57 left in the first quarter.
The team's big offseason acquisition hadn't played since Nov. 19 after undergoing left wrist surgery.
Millsap was emotional at Tuesday morning's shootaround, tearing up as he thought about the prospect of his return being so close.
"I feel like I'm a tough guy," Millsap told reporters. "For something that significant to happen, it means a lot to get to this point from where I was."