Myers gets a five-year, $30 million deal, while Benn signed for two years and $4 million.
The 29-year-old Myers became a free agent after completing a seven-year, $38.5 million contract that he originally signed with the Buffalo Sabres and finished with the Jets following a February 2015 trade.
The big defenseman, listed at 6-foot-8, 229 pounds, had said in April that he was open to a return to Winnipeg. This offseason, the Jets traded fellow defenseman Jacob Trouba, a restricted free agent, in large part because they wouldn't have the cap space to sign both.
Myers has totaled 74 goals and 191 assists in 635 career games. He has never again reached the numbers of his rookie season in 2009-10, when he finished with 11 goals and 37 assists and won the Calder Memorial Trophy as rookie of the year.
He had nine goals and 22 assists last season.
The 31-year-old Benn had five goals and 17 assists for a career-high 22 points for the Canadiens last season, his third with the team after a 2017 trade from Dallas.
Benn also was a career high plus-15 last season.