Four fire engines and around 25 firefighters were called to a fire at a block of flats on Wesley Close in South Harrow.
A flat on the second floor of a three-storey block was destroyed by the blaze. There were no reports of any injuries.
The Brigade was called at 1334 and the fire was under control by 1437. Fire crews from Harrow, Wembley, Stanmore and Park Royal fire stations were at the scene.
The cause of the fire is under investigation.