Beaulieu, 22, had one goal and eight assists in 64 games this past season.
The 6-foot-1 185-pound Beaulieu is set to earn $1 million per season, a slight increase on the $925,000 he made in 2014-15 in the final season of a three-year entry-level contract. He can become a restricted free agent in 2017-'18.
In 87 NHL games, Beaulieu has one goal and 12 assists. He has three assists in 12 playoff games.
Montreal drafted Beaulieu 17th overall in 2011 from the Saint John Sea Dogs.