Antetokounmpo played just 46 seconds. On a driving layup, he appeared to step on the foot of Kelly Olynyk, rolling what was already an injured ankle. He limped to the locker room and spent a few minutes there before returning to the bench, where he sat for the rest of the game.
Antetokounmpo entered the game listed as probable with a right ankle sprain.
Bucks coach Mike Budenholzer said the new injury was a sprain and that the team is hopeful it's not serious. Budenholzer said the team would see how the ankle responds to treatment and go from there.
Milwaukee next plays the Bulls in Chicago on Friday night.
The Associated Press contributed to this report.