Four fire engines and 21 firefighters and officers were called to a fire at a terraced house in Butler Road, West Harrow.
Half of the ground floor was damaged by the fire and a first floor bay window collapsed. One man left the property before the arrival of the Brigade. He was taken to hospital by London Ambulance Service crews suffering smoke inhalation.
The Brigade was called at 1753 and the fire was under control at 1853.
The cause of the fire is under investigation.