Therrien was in the fifth season of his second tenure as coach of the Canadiens (31-19-8), who lead the Atlantic Division with 70 points but are 1-5-1 in their past seven games. Since starting the season 13-1-1, they are 18-18-7.
The Canadiens are in the middle of a five-day break. Their next game is against the Winnipeg Jets at home Saturday (2 p.m. ET; CBC, SN, TVA Sports, NHL.TV). Their first practice under Julien is scheduled for Friday.
Montreal required permission from Boston to speak with Julien because he had one year remaining on his contract with the Bruins prior to being fired Tuesday.
This is the second straight season the Canadiens have gotten off to a hot start only to cool off. Montreal won its first nine games and was 17-4-2 on Nov. 25, 2015, when goaltender Carey Price was lost for the season because of a knee injury. The Canadiens went 21-34-4 the rest of the season and missed the Stanley Cup Playoffs.
READ: Claude Julien NHL timeline
Bergevin made several moves in the offseason to try to keep that from happening again, most notably trading defenseman P.K. Subban to the Nashville Predators for defenseman Shea Weber on June 29. Bergevin also acquired forward Andrew Shaw from the Chicago Blackhawks, signed forward Alexander Radulov as a free agent, and traded center Lars Eller to the Washington Capitals.
The Canadiens had to deal with significant injuries to center Alex Galchenyuk, right wing Brendan Gallagher and defenseman Andrei Markov in December and January, a contributing factor in Montreal's mediocre record over the past 2 1/2 months. But when players returned to health, the Canadiens did not start winning again. They lost back-to-back games over the weekend, 4-2 to the St. Louis Blues at home on Saturday and 4-0 at the Bruins on Sunday.
The loss in Boston on Sunday was the third time in five games the Canadiens were shut out.
"As a player, especially as the captain, you feel guilty," Canadiens left wing Max Pacioretty told Sportsnet on Tuesday. "Ultimately, if we had performed better, especially as of late, then you don't force management to have to make a decision like this. We definitely have been underperforming as of late, but I feel it's on the players. We've seen around the League this tends to be the result when teams don't step up and perform. I have nothing but great things to say about Michel, and that's what makes this pretty tough for me."
Gallagher repeated something Price said following the loss in Boston, something that is difficult for any coach to hear from his players.