The London Fire Brigade (LFB) responded to reports of a fire at a block of flats on Ellis Road.
Four fire engines and around 25 firefighters attended the scene.
The fire damaged half of a second floor.
The London Ambulance Service took one woman to hospital.
Her condition is not known.
The LFB received the first of three calls just after 3.40am, and crews from Purley, Wallington, Croydon, and Mitcham fire stations were dispatched.
The fire was extinguished by 4.12am.
The fire is being treated as accidental and is believed to have been caused by items left on a cooker hotplate.
