The Canucks, clinging to the eighth spot in the Western Conference standings, suffered their sixth loss in a row.
Pacioretty delivered a power-play goal with 5:01 left in the opening period to put the Canadiens in front for good, tallied early in the third to give Montreal a 3-1 lead and then scored into an empty net with 1:08 remaining.
Montreal won for the fourth time in six games with Carey Price stopping 42 shots. The other Montreal goals came from Ryan White in the first period and Tomas Plekanec in the third. White's goal was his first of the season.
Roberto Luongo gave up four goals on 28 shots.
The win allowed Montreal to keep pace with Toronto in their tie for third place in the Atlantic Division and they moved within one point of second-place Tampa Bay.