Four fire engines and around 25 firefighters responded to a fire on Denmark Road, Camberwell.
The fire was located in a second floor flat, in a residential block of four floors. Part of the flat was damaged by the fire.
The Brigade was first called about the fire at 1259, and crews from Brixton, Peckham and Soho fire stations are at the scene. Firefighters had the incident under control by 1330.
The cause of the fire is not yet known.