Four fire engines and around 25 firefighters were called to a fire at a derelict house on Elms Road in Harrow.
Part of the first floor and roof of a detached house were damaged by fire. There were no reports of any injuries.
The Brigade was called at 0040 and the fire was under control by 0226. Fire crews from Stanmore, Harrow and Northolt fire stations attended the scene.
The cause of the fire is under investigation.