Brassard, who was stopped on a penalty shot in the game's second minute, didn't miss on his later chance. He one-timed a Guentzel pass for a power-play goal at 2:38 of the third period to break a 3-3 tie.
Brassard reached the 20-goal plateau for the second time in his career, and second-place Pittsburgh moved to within two points of the first-place Washington Capitals in the Metropolitan Division.
Guentzel added his goal with 1:33 left, with Sidney Crosby collecting career assist No. 700 on the play.
Goalie Casey DeSmith made 27 saves in the victory. Crosby, Evgeni Malkin and Patric Hornqvist also each scored once for Pittsburgh.
The Canadiens, who dropped their fourth straight, got a lift when goalie Carey Price returned after missing 14 games with a concussion sustained on Feb. 20. Price finished with 34 saves, including the penalty-shot stop.
Jonathan Drouin, Nikita Scherbak and Jacob de la Rose lit the lamp for Montreal.
Malkin and Hornqvist both scored first-period goals for the Penguins, who fired 16 shots at Price and came away with a 2-1 lead after one.
Malkin got knocked to the ice in front of Price and still got the puck in at 9:53. Hornqvist scored on a wrist shot from between the circles with 2:39 left in the period for a 2-0 lead.
However, Montreal scored when Drouin banged in a puck out of the air with 30 seconds left in the opening period.
The Canadiens tied it on a short-handed Scherbak goal at 8:19 of the second period and took a 3-2 lead when de la Rose scored at 14:24.
That lead did not last long because Crosby scored spectacularly just 38 seconds later, and the second period ended at 3-3. Crosby basically passed the puck to himself by batting it out of mid-air and then flicking a backhander out of mid-air past Price.
The Penguins scored the game's final three goals.
--Field Level Media
Montreal | Pittsburgh | |
Jacob De La Rose 1 | Points | Jake Guentzel 3 |
Jacob De La Rose 1 | Goals | Jake Guentzel 1 |
Jordie Benn 1 | Assists | Jake Guentzel 2 |
N/A | Power Play Goals | Derick Brassard 1 |
Nikita Scherbak 1 | Short Handed Goals | N/A |
Carey Price .872 | Save Percentage | Casey DeSmith .900 |
Carey Price 34 | Saves | Casey DeSmith 27 |
Team | Shots | Goals | Power Play | Penalty Kill | Penalty Mins | Face Offs Won |
Montreal | 30 | 3 | 0-3 | 1-3 | 11 | 34 |
Pittsburgh | 39 | 5 | 2-3 | 3-3 | 11 | 39 |