Gagnon is wanted for threatening to kill his spouse.
"He communicated many times in the last three months with her and in one of the conversations with her he made some clear death threats," said Const. Simon Delorme with the Montreal police.
Police said they believe he could be in Montreal, Quebec City, or possibly Rimouski.
Gagnon is 5 feet 11 inches and weighs 190 pounds.
If you've seen him, police say you should call 911.