Six fire engines and around 40 firefighters were called to a fire at a house on Northumberland Road in Harrow.
Half of the ground floor and most of the first floor of a semi-detached house were damaged by the fire. A small part of an adjoining semi-detached house were also damaged. There were no reports of any injuries.
The Brigade's 999 Control Officers took 18 calls about the fire.
The Brigade was called at 1840 and the fire was under control by 2204. Fire crews from Harrow, Northolt and Wembley fire stations were at the scene.
The cause of the fire is under investigation.