It started just after midnight at La Cantina, on St Laurent boulevard. Police received a 911 call at 12:50 a.m.
Police say they have reason to believe the fire was intentional.
"Some witnesses reported to the officers that they may have seen one or many individuals leaving, rapidly, the scene of the crime right before the start of the fire," said Manuel Couture, with the Montreal police.
About 100 firefighters were called to the scene to battle the flames.
Couture says the building sustained "major" damage.
And two people were taken to hospital after a Fire Department supervisor's vehicle collided with a city bus while on its way to the scene. They are being treated for non-life-threatening injuries.