Six fire engines and around 40 firefighters were called to a fire at a house on Crownhill Road in Harlesden.
The first floor and roof of an end of terrace house were destroyed by the fire and most of the ground floor was damaged. Two men left the building before the Brigade arrived. One man was treated on scene by London Ambulance Service crews and taken to hospital.
The Brigade's 999 Control Officers took 12 calls to the fire.
The Brigade was called at 0858 and the fire was under control by 0941. Fire crews from Park Royal, Willesden, North Kensington and Wembley fire stations were at the scene.
The cause of the fire is under investigation.