Four fire engines and around 25 firefighters tackled a fire at a house on Grant Road in Wealdstone.
Part of a loft conversion, in a mid-terraced house converted into flats, was damaged by fire. There were no reports of any injuries.
The Brigade's 999 Control Officers received six calls about the fire.
The Brigade was called at 1500 and the fire was under control by 1616. Crews from Harrow, Stanmore, Park Royal and Acton fire stations attended the scene.
The cause of the fire is under investigation.