Winslow intentionally stepped on Embiid’s mask after it had fallen onto the court with 7:51 remaining in the second quarter of the 76ers’ 128-108 victory on Thursday night.
The NBA cited Winslow for unsportsmanlike conduct in announcing the penalty Friday.
Embiid was wearing the mask for the first time after returning from a 10-game absence caused by a broken orbital bone around his left eye.
Philadelphia leads the series 2-1. Game 4 is Saturday.