Six fire engines and around 40 firefighters were called to a fire at a flat in Peel Road in Wealdstone.
Half of a second floor flat was damaged by fire.
The Brigade was called at 1819 and the fire was under control at 1950. Fire crews from Harrow, Stanmore, Northolt and Wembley fire stations attended the scene.
The cause of the fire is believed to be accidental.