Four fire engines and around 25 firefighters were called to a fire at a fast-food takeaway shop with flats above on High Road in Wembley.
Half of the ground floor was damaged by fire and part of the extraction system from the ground floor to the roof of the building was also damaged by the blaze. Around 30 people left the building before the Brigade arrived. There were no reports of any injuries.
The Brigade's Fire Investigators believe the fire was accidental and involved cooking with hot oil.
A London Fire Brigade spokesperson said: "Cooking with hot oil can be really dangerous and the risk increases when you start frying food more than once.
“All it can take is for you to become distracted for a few seconds and your cooking oil can quickly go up in flames.
“You should never leave cooking on the hob unattended."
The Brigade was called at 1212 and the fire was under control by 1310. Fire crews from Wembley, Park Royal and Northolt fire stations attended the scene.