Four fire engines and around 25 firefighters were called to a flat fire on Westbourne Grove in Paddington.
Part of a four-roomed flat on the fourth floor above a shop was damaged by fire. One woman was taken to hospital after suffering from smoke inhalation.
A London Fire Brigade spokesperson said: “On arrival, crews could see a large amount of grey smoke coming from the building.
“A crowd had gathered outside and a member of the public called 999. A man left the affected flat on arrival of firefighters.”
The Brigade was called at 0859 and the fire was under control by 0925. Fire crews from Paddington, Kensington and North Kensington fire stations attended the scene.
The cause of the fire has been recorded as undetermined.