The Canadiens had lost six in a row and had dropped seven of their first eight, their worst start to a season in 70 years. Five of the seven losses had come at home -- the first time Montreal had lost its opening five home games since the proud franchise began playing in 1917.
The poor start cost assistant coach Perry Peam his job earlier in the day, although Jacque Martin was retained as the team's head coach.
Jaromir Jagr put Philadelphia in front midway through the first period, but Yannick Weber tied it on the power play with 3 seconds left in the opening stanza.
Andrei Kostitsyn put the Canadiens in front 10:26 into the second period and Pacioretty produced the next two goals -- coming with 7:22 having gone by in the second and 3:16 into the third.
Mike Cammalleri finished the scoring for the Canadiens, who had averaged barely two goals a game while compiling a 1-5-2 record.
Philadelphia suffered its first road loss of the year after winning its first three away from home.
2014: The Year in Music [PHOTOS]