The incident took place in a 24-storey building on the corner of Atwater Avenue and de Maisonneuve Boulevard around 3:30 a.m.
Authorities say the fire started on the building's 10th floor.
The building's upper floors were evacuated but the fire did not spread to other apartments. Some other units did sustain smoke damage.
Three people had minor injuries and firefighters had to rescue a man from a balcony.
Atwater Avenue remains closed between Sainte-Catherine Street and de Maisonneuve Boulevard.
Officials allowed people to get back to their homes around 6 a.m. More than 700 people live in the building.
The cause of the fire is not known.