The fire started around 9:45 p.m. Tuesday night in a building near the intersection of Rouen Street and Darling Street.
Police spokesperson André Leclerc says the man suffered burns to about a third of his body.
"The next 24 hours will be critical in his condition," said Leclerc.
As well, a 40-year-old woman was treated for smoke inhalation.
Leclerc says damage was limited to one apartment, and the other tenants have been allowed to return to their homes.
The cause of the fire has not been confirmed, but police are investigating.