General manager Marc Bergevin said he informed all three Friday. Bergevin said "they did great service for our team," and "on the leadership side, these guys really helped with the transition."
The 41-year-old Gonchar had one goal and 12 assists in 45 games and helped Nathan Beaulieu develop into a regular NHL defenseman.
Malhotra, a 34-year-old center, had a goal and three assists in 41 games. Defenseman Weaver, 37, had four assists in 31 games.
None of them played in the postseason. Montreal's season ended with a second-round elimination by the Tampa Bay Lightning.
Bergevin defended coach Michel Therrien, saying he expects his entire coaching staff to return.