Four fire engines and around 25 firefighters tackled a fire at a social club on Dulwich Common.
Part of the single-storey building and the roof were damaged by fire. There were no reports of any injuries.
The Brigade was called at 0113 and the fire was under control by 0313. Fire crews from Forest Hill, West Norwood and Brixton fire stations attended the scene.
The cause of the fire is under investigation.