Four fire engines and around 25 firefighters were called to a workshop fire on Harcourt Road in Wallington.
Part of a single-storey furniture restoration workshop was damaged by fire. There were no reports of any injuries.
The fire is believed to have been accidental and caused by a discarded cigarette.
Sub Officer Orrin Justin, who was at the scene, said: “The fire had started in some rubbish at the rear of the property and spread to the fencing and up the building.
“Crews gained access quickly and prevented further damage to the workshop.
“If you are a smoker, it’s absolutely vital that you ensure your cigarette is completely out when you’ve finished smoking it.
“Make sure smoking materials are cold before emptying ashtrays. Preferably wet stubs before throwing them into a bin.”
The Brigade was called at 2255 and the fire was under control by 2351. Fire crews from Wallington, Croydon, Sutton and Mitcham fire stations attended the scene.