Four fire engines and around 25 firefighters were called to a fire at a flat on Churchill Gardens in Pimlico.
Part of a flat on the ground floor of a five-storey block was damaged by the fire. Firefighters wearing breathing apparatus rescued a woman from the ground floor. She was treated at the scene for smoke inhalation by London Ambulance Service crews and taken to hospital.
The Brigade was called at 1342 and the fire was under control by 1422. Fire crews from Lambeth, Dowgate and Soho fire stations were at the scene.
The fire is believed to be accidental.