Four fire engines and 21 firefighters and officers were called to a fire at a block of maisonettes in Maundeby Walk, Neasden.
A two-storey maisonette on the ground and first floor was damaged by fire.
The Brigade was called at 1650 and the fire was under control at 1750. Fire crews from Willesden, Hillingdon and Park Royal fire stations attend e scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.