Ten fire engines and around 70 firefighters were called to a fire at a derelict building on Coventry Close in Kilburn.
The whole of the ground floor in the three storey building was alight. Four people were helped to safety by fire crews at the rear of the building.
Station Commander Kevin Morgan was in attendance, he said: "Due to heavy smoke, local residents were advised to keep their windows and doors shut.
"Motorists were advised to avoid the area due to a road closure on Kilburn High Road between Belsize Road and Oxford Road."
The Brigade's 999 Control officers received the first calling alerting them to the fire at 1443. They mobilised crews from West Hempstead, North Kensington, Paddington, Chelsea, Bethnal Green and Willesden fire stations. The fire was under control by 1603.
The cause of the fire is under investigation.