Emergency crews were called just before 12 a.m. Tuesday after the fire was discovered at Dragon Flowers, which occupies the main floor of a three-storey building on Bernard Street.
Montreal Fire operations chief Sylvain Cuillerier said the fire appears to have started in the ceiling.
He said firefighters quickly brought the fire under control.
Damage was limited to the street-level flower shop and apartments on the first floor.
No one was injured and the fire doesn't appear to be suspicious, officials said.