Joel Armia scored the go-ahead goal late in the first period, and Nick Suzuki scored for the Canadiens (27-32-12), who have won two straight and are 2-2-1 in their past five games.
Montreal coach Martin St. Louis returned after being away from the team since March 16 because of family reasons.
Nathan MacKinnon scored to extend his home point streak to 35 games and overall point streak to 19 games for the Avalanche (46-21-5), who had won 11 of their past 12 (11-1-0). Justus Annunen made 25 saves.
MacKinnon has 77 points (29 goals, 48 assists) during his season-opening home streak, which is the second-longest in NHL history. Wayne Gretzky owns the longest at 40 games (Los Angeles Kings, 1988-89). MacKinnon also became the first player in NHL history to have two different point streaks of 19 or more games in the same season.
MacKinnon gave Colorado a 1-0 lead 43 seconds into the first period on a one-timer from the right circle. Mikko Rantanen made a shovel pass at the left side of the net, floating the puck across to MacKinnon.
Suzuki scored nine seconds later to tie it 1-1 at 52 seconds when he slipped a check from Casey Mittelstadt at the blue line, skated in alone on Annunen and sent a wrist shot five-hole.
Juraj Slafkovsky had an assist on the goal to extend his point streak to eight games (two goals, six assists).
Armia extended it to 2-1 at 14:53 after he located a loose puck behind Annunen and took it behind the net for the wraparound.
