Four fire engines and around 25 firefighters were called to a fire at a flat on Denzil Road in Willesden.
The first floor and roof were destroyed by fire. Part of the ground floor was damaged.
The Brigade was called at 1923 and the fire was under control by 2152. Fire crews from Park Royal, North Kensington, Wembley, and Paddington fire stations attended the incident.
The cause of the fire is under investigation.