Four fire engines and around 25 firefighters were called to a flat fire above a cafe on London Road in Morden.
A small part of the first floor flat was destroyed by fire.
One woman suffering from smoke inhalation was treated on scene by fire crews.
The Brigade was called at 1339 and the fire was under control by 1440. Fire crews from Wimbledon, Sutton, Tooting and Sutton fire stations were in attendance.
The cause of the fire is under investigation.