Emergency crews say they found smoke coming from the building at 99 Sunnylea Cres. when they arrived at around 11 p.m.
Officials said crews quickly extinguished a smouldering mattress and removed it from the building.
The structure was evacuated, according to the fire department. Residents were reportedly forced onto a Guelph Transit bus while the building was ventilated, but they were eventually allowed to go back inside, fire officials said.
The tenant of the apartment unit and a Guelph police officer were taken to hospital for treatment of smoke inhalation, according to fire officials.
A Guelph police spokesperson said the officer, who was first on the scene, ran into the building to get the tenant out. The officer was treated and released soon after.
No other injuries were reported.
Officials said the cause of the fire was due to careless smoking in bed, but it’s unclear whether any charges will be laid.