Four fire engines and around 25 firefighters tackled a flat fire on Comeragh Road in West Kensington.
Most of a four-roomed flat on the ground floor of a converted end-of-terrace house was damaged by fire. Half of the communal area was also damaged by the blaze. Four people left the building before the Brigade arrived and three people were taken to hospital by London Ambulance Service crews.
The Brigade was called at 0137 and the fire was under control by 0402. Fire crews from Hammersmith, Kensington, Fulham and Heston fire stations attended the scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.