Gilles Meloche went missing on Sunday night and is still at large.
He is 56 and has been behind bars since 1980 for second-degree murder, attempted murder, kidnapping, robbery and armed robbery.
Staff at the Montee St-Francois federal prison say Meloche is five-foot-seven and 240 pounds with blue eyes, shaved brown hair and wears black-framed glasses.
He has a skull tattoo on his right arm, a heart tattoo and a genie tattoo on his left arm and a scar on his left hand.
An inmate identified as Phillipe Pelletier fled the facility last week and has not yet been found.