Four fire engines and around 25 firefighters were called to a fire at a derelict house on Beckenham Place Park in Beckenham.
Part of the first floor of the detached property was damaged by the fire. There were no reports of any injuries.
Beckenham Sub Officer Sophie Willcocks, who was at the scene, said: "Crews initially tackled the blaze from the outside and firefighters wearing breathing apparatus were then committed to fight the fire internally.
"There were some mattresses alight in a room on the first floor and crews worked quickly to limit the damage and stop the blaze spreading from the room of origin."
The Brigade was called at 1843 and the fire was under control by 2017. Fire crews from Beckenham, Bromley, Woodside and Forest Hill fire stations were at the scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.