Eight fire engines and around 60 firefighters were called to a fire at a patisserie on Edgware Road, W2.
Part of a restaurant on the ground floor of a parade of shops and offices was damaged by the fire. There were no reports of any injuries.
Station Commander Matt Williams, who was at the scene, said: "The fire broke out in a ground floor restaurant and crews worked hard to bring it under control.
"The blaze involved the restaurant's ducting (extraction) system.
"One of the Brigade's 32m ladders was in use as an observation tower.
"Edgware Road was closed and there was heavy traffic nearby so we advised people to avoid the area where possible."
The Brigade was called at 1109 and the fire was under control by 1438. Fire crews from Paddington, Euston, Soho and Kensington fire stations were at the scene.
The fire is believed to have been accidental and caused by an electrical fault.