Bergevin signed rugged left-winger Brandon Prust from the New York Rangers to a US$10-million, four-year contract and inked right-winger Colby Armstrong from the Toronto Maple Leafs to a $1-million, one-year deal.
They also brought back veteran defenceman Francis Bouillon from the Nashville Predators for $1 million over one year.
The Canadiens only confirmed the Prust signing, although Armstrong announced his contract himself on Twitter and Bouillon spoke about his new deals with various media.
Prust said he had mixed emotions in leaving New York after three seasons but joining a team that welcomes a tough forward.
The London, Ont., native said he will complement Montreal's recent re-signings of physical forwards Travis Moen and Ryan White. And he will have a coach who appreciates toughness in Michel Therrien, who returned to Montreal in May to replace Randy Cunneyworth.
''I think having me there is important and will make our jobs easier moving forward,'' said Prust. ''That's something I got out of our conversations. They wanted to add a bit of grit.
''It's good to have a little more team toughness. Other teams coming into our building will know they're in for a long night.''
He will also be closer to his girlfriend, who works in television in Montreal.
Prust said he spoke to Rangers coach John Tortorella on Sunday and was sad to go, but felt the offer from Montreal was better.
"In the end, (the Rangers) weren't close to where Montreal was,'' he said. ''Montreal showed a lot more interest.
''I felt I fit into their lineup. The team is moving in the right direction and I wanted to be part of that.''
A team spokesman said Bergevin was still working on deals and would not talk to the media until Monday.
The club also signed free agent forward Michael Blunden and goaltender Cedrick Desjardins to one-year, two-way contracts.
The Canadiens were looking to add muscle to their checking lines and an extra defenceman, and that's what they got.
They are also seeking a forward for their top two lines, amid speculation they may be interested in former Pittsburgh star Jaromir Jagr.
The six-foot, 195-pound Prust played in all 82 games the last two seasons in New York. His production dipped from 13 goals and 29 points two years ago to five goals and 12 assists last year.
The 28-year-old former London Knight, a strong penalty killer, is going into his fifth NHL season. He was drafted 70th overall in 2004 by Calgary.
Both Armstrong and Bouillon have a history with Therrien, who coached Bouillon in junior hockey in Laval and Granby as well as during his first stint as Canadiens coach a decade ago. Therrien had Armstrong with the Pittsburgh Penguins.
The six-foot-two, 187-pound Armstrong, a pesky, physical forward, became a free agent when the final year of his contract was bought out by the Leafs. He will actually earn $2 million next season, with half paid by Toronto.
The 29-year-old broke into the NHL with the Penguins in 2005-06 and played in Atlanta before joining the Leafs two seasons ago. His time in Toronto was marked by injuries as he played only 29 games last season, picking up a goal and a two assists and was minus-8.
The five-foot-eight, 201-pound Bouillon, a Montreal native, is deceptively strong and can play a physical game. The 36-year-old played his first 10 seasons with the Canadiens before moving to the Predators in 2009, appearing in 66 games last season with four goals and seven assists.
The 25-year-old Blunden, acquired last July from Columbus, had two goals and two assists in 39 games for Montreal last season. He missed 20 games with a knee injury suffered Feb. 2.
Desjardins, 26, spent last season with the AHL Lake Erie Monsters, going 16-11-5 with a 2.11 goals-against average and .932 save percentage. He was in the Montreal organization from 2006 to 2010 before moving to Tampa Bay, where he posted two wins in as many games. He will likely fit in behind Carey Price and Peter Budaj in the organization's depth chart.
In the days leading up to the opening of the free agent market, Bergevin signed some potential free agents, including Moen, White, depth centre Petteri Nokelainen and defenceman Alexei Emelin.
He is working on new deals for a handful of restricted free agents, including Price and defenceman P.K. Subban.