Four fire engines and around 25 firefighters tackled a fire at a restaurant with flats above on Headstone Drive in Harrow.
Half of a ground-floor extension was destroyed by fire. Three people left the property before the arrival of the Brigade. There are currently no reports of any injuries.
The Brigade was called at 1116 and the fire was under control by 1223. Crews from Stanmore, Northolt and Wembley fire stations attended the scene.
The cause of the fire is under investigation.