The NHL team posted the news Tuesday on Twitter. He took a hit from Ottawa's Erik Karlsson in the second period of Montreal's 2-1 overtime win on Sunday.
Beaulieu has one assist in three playoff games. He had one goal and eight assists in 64 regular-season games.
Coach Michel Therrien says Greg Pateryn will replace Beaulieu in the lineup. Pateryn didn't have a point in 17 games this season.
Montreal can wrap up a four-game sweep with a victory Wednesday night at Ottawa.
The Canadiens also announced they'll play a preseason game against the Pittsburgh Penguins at the Videotron Centre on Sept. 28 in Quebec City.