Pittsburgh won for the fourth time in six games and had to rally from a one-goal deficit to get the victory.
Dupuis scored the game-winning goal after taking a rink-wide pass from Brooks Orpik. Dupuis fired a slap shot from the top of the left circle that got past Carey Price.
Price stopped 38-of-41 shots. Marc-Andre Fleury had to make just 19 saves to get the win.
Pittsburgh has defeated Montreal three times this year and has outscored the Canadiens in those games 12-4.
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