Four fire engines and around 25 firefighters were called to a fire at a flat on Beechwood Avenue in Richmond upon Thames.
Part of a ground floor flat in the two storey building was damaged by fire. Part of a maisonette above was damaged by smoke.
A member of the public spotted smoke coming from the ground floor and called the Brigade. One woman was treated by London Ambulance Service crews for smoke inhalation.
The Brigade was called at 2041 and the fire was under control by 2151. Fire crews from Richmond, Chiswick and Heston fire stations attended the scene.
The cause of the fire is believed to be accidental.