Four fire engines and around 25 firefighters were called to a house fire on Manor Farm Road in Wembley.
Half of the first floor and most of the roof of a mid-terrace house were damaged by the fire. One woman left the building before the Brigade arrived. She was treated on scene for smoke inhalation by London Ambulance Service crews.
The Brigade was called at 1129 and the fire was under control by 1321. Fire crews from Wembley, Acton and Park Royal fire stations were at the scene.
The cause of the fire has been recorded as undetermined.