The move, made two days before the NHL trade deadline, came a month after the Canadiens picked up Nikita Nestorov from the Tampa Bay Lightning for a sixth-round pick.
Benn, the older brother of Dallas All-Star Jamie Benn, is a left-shot defenceman who can also play on the right side. With Pateryn’s departure, the Montreal roster has only Shea Weber and Jeff Petry as natural righties.
"In Jordie Benn, we get an experienced NHL defenceman and a player who will solidify our defensive group," Canadiens general manager Marc Bergevin said. "While providing stability in our end, he can also contribute offensively."
The 6-foot-2, 200-pound Benn has two goals and 13 assists and is minus-3 in 58 games. The 29-year-old Victoria native has 11 goals and 60 assists in 302 games.
He signed a $3.3 million, three-year extension last June.
Benn, who will take over Pateryn’s jersey No. 8 in Montreal, usually plays on a second or third pairing and can help kill penalties. He averaged 18:37 of ice time per game this season in Dallas.
The 26-year-old Pateryn had one goal and five assists in 24 games. He missed time earlier in the season with an ankle injury and has been a healthy scratch at times. The physical 6-foot-2, 223-pound native of Sterling Heights, Michigan, has two goals and 11 assists in 82 games.
He is signed through the 2017-18 season with an annual cap hit of $800,000.
"Greg is a solid defender and possesses a physical presence on the back end," Stars general manager Jim Nill said. "He brings size and another right shot into the mix for us."
A report last week said Pateryn had been offered to the league’s 29 other teams. He would not say whether he asked for a trade, but denied that he was unhappy in Montreal.
"I felt I was a little stuck in the mud. That’s why sometimes change is good," he said. "There was no reason to be unhappy with anything in Montreal. Sometimes you just need fresh faces and a fresh start. That’s what’s going to be best for me."
The fifth-year Canadien had some strong games early in the season, but then missed 24 games when he injured an ankle on Dec. 6. He was scratched for six of the team’s 11 games since he returned on Jan. 31.