Nino Niederreiter and Dany Heatley scored for the Wild (13-5-4), which ended a four-game winning streak and an eight-game undefeated run dating to a 5-1 loss to Chicago on Oct. 28. Minnesota plays Wednesday night in Ottawa.
Wild starter Josh Harding, one of the NHL's three stars for his three wins last week, was pulled in the second period after allowing three goals on 19 shots in favour of Darcy Kuemper. Harding has given up three only twice this season, both times to Montreal.
Pacioretty had not scored in 10 games since Oct. 12 in Vancouver, although he missed eight games with a leg injury during that stretch. His line with centre David Desharnais had been taking heat for not producing.
That ended 2:57 into the second period, when Pacioretty had a Desharnais pass go in off his skate from in front of Harding.
The Canadiens, coming off a 1-0 loss at home to the New York Rangers on Saturday night, had not scored since a Lars Eller goal at 7:34 of the second period of a 3-2 shootout win last Friday in Columbus.
Pacioretty converted a spin-around pass from Desharnais at 10:06 at even strength and then ended Harding's night when he tipped in P.K. Subban's point shot on a power play at 13:36.
Bournival came from behind the net and beat Kuemper inside the near post at 16:16. Briere one-timed Brian Gionta's cross-ice pass behind Kuemper on a counter attack 4:42 into the third.
Galchenyuk converted an Andrei Markov feed on a power play at 7:35. Heatley jammed in a goal on a power play with two seconds left in the game.
Notes: Six goals was a season high scored for Montreal and allowed by Minnesota. . . Pacioretty got his second career hat-trick (last: Feb. 9, 2012). . . Winger Rene Bourque (lower body) sat out and Ryan White returned to the Montreal lineup. . . Douglas Murray and George Parros were scratched. . . Minnesota sat out defenceman Matt Dumba. . .The Wild started a four-game road trip that takes them to Ottawa on Wednesday, Winnipeg on Saturday and St. Louis on Monday.