Raymond Rouette, an inmate at the minimum-security Ste-Anne-des-Plaines Institution, escaped at about 7:30 p.m. Thursday.
He has been serving an indeterminate sentence since February, 1988 for first-degree murder.
Rouette is 51 years old and about five-foot-five, 152 pounds, with brown eyes, brown hair and a scar on his left eye.
The Correctional Service of Canada has contacted Montreal police and a warrant has been issued for his arrest.
The Correctional Service says it will be conducting a joint investigation with prison officials into the circumstances behind the escape.