Four fire engines and around 25 firefighters were called to a fire at a flat on Pages Walk in Elephant and Castle.
Part of a four roomed flat on the ground floor was damaged by fire. Three adults and two children left the building before the Brigade arrived. They were treated on scene after suffering from smoke inhalation.
The Brigade was called at 1818 and the fire was under control by 1902. Fire crews from Old Kent Road, Peckham, New Cross and Deptford fire stations attended the scene.
The cause of the fire is believed to have involved an electrical supply.