Four fire engines and around 25 firefighters were called to a fire at a flat on Hilton Close in Uxbridge.
Half of a five-roomed flat on the first floor of the building was damaged by fire. One man was treated on scene by London Ambulance Service crews and taken to hospital.
The Brigade was called at 0430 and the fire was under control by 0529. Fire crews from Hillingdon, Hayes and Heathrow fire stations attended the scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.