Rod Thorn, president of basketball operations for the NBA, said in an official statement that Mayo "has been suspended one game without pay for forcibly striking" Stiemsma.
Mayo, who will sit out the Bucks' game against the Washington Wizards on Saturday night, was assessed a flagrant foul 2 and ejected with 1 minute 52 seconds left in the first quarter after he punched Stiemsma, who had set what appeared to be a clean screen for teammate Anthony Morrow.
The Pelicans went on to win the game, 112-104, in overtime.
Mayo, 26, is a six-year veteran with his third team in three seasons. He's averaging 11.8 points, 2.4 rebounds and 2.2 assists a game this season. He has career averages of 14.8 points, 3.3 rebounds and 3.0 assists a game.
Mayo, who is 6-foot-4, averaged 20.4 points, 4.5 rebounds and 3.3 assists a game in 2007-08 for USC, which went 21-12 and lost in the first round of the NCAA tournament to a Kansas State team that featured Miami Heat forward Michael Beasley. The Trojans later vacated all their victories for the season when it was determined that Mayo had received improper benefits before attending USC.