Montreal had a four-game winning streak halted.
The Canadiens overcame a 3-1 deficit with three straight goals, the last of which came from Roman Hamrlik on the power play 3:25 into the third period.
But Malkin and Gonchar scored 36 seconds apart to rally the Penguins.
Malkin delivered on a wrist shot for his 35th goal of the season and Gonchar won it with a power-play goal that came on a slapshot from the blue line. It was the 600th point of Gonchar's career.
The outcome tied the season series at 2-2.
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