Five fire engines and 31 firefighters and officers were called to a fire at a block of flats in Edgware Road in Paddington.
Part of a flat on the third floor of the building was damaged by fire. Two adults and two children left the property before the arrival of the Brigade and were treated at the scene for smoke inhalation before being taken to hospital by London Ambulance Service crews.
The Brigade was called at 1840 and the fire was under control at 1921. Fire crews from Paddington, Euston, Soho and Kensington fire stations attended the scene.
The cause of the fire is under investigation.