Four fire engines and around 25 firefighters were called to a fire at a house on Fraser Road in Perivale.
Half of the ground floor of a mid-terraced house was damaged by fire. The rear extensions of two neighbouring properties were also damaged by fire.
Three men left the property before the arrival of the Brigade. One man was treated at the scene for smoke inhalation by London Ambulance Service crews.
The Brigade was called at 0155 and the fire was under control by 0315. Fire crews from Wembley, Park Royal and Acton fire stations attended the scene.
The cause of the fire is under investigation.