Simmons will serve the suspension Wednesday for the season opener against the New Orleans Pelicans.
Coach Doc Rivers threw Simmons out of practice Tuesday and the suspension came shortly thereafter, sources tell ESPN's Adrian Wojnarowski.
The three-time All-Star guard was a holdout in training camp in the wake of his offseason trade demand. He reported last week and practiced Sunday and Monday with the Sixers.
He had been scheduled to talk to the media on Tuesday.
The 25-year-old from Australia has four years and $147 million left on his max contract.
The Associated Press contributed to this report.