Two fire engines were called to a fire at a flat in Astonville Street, Southfields last night.
Part of a flat on the first floor of the building was damaged by fire.
A woman was rescued by firefighters wearing breathing apparatus and was taken to hospital by London Ambulance Service.
The fire is believed to have been caused by discarded smoking materials.
A spokesperson for the London Fire Brigade said: "Incidents like this show how important it is to dispose of cigarettes properly. It’s absolutely vital you ensure your cigarette is completely out when you’ve finished smoking it. If you don’t, you risk causing a fire that could destroy not only your home, but also your life."
The Brigade was called at 1924 and the fire was under control at 2024. Fire crews from Wandsworth and Battersea fire stations attended the scene.