Four fire engines and around 25 firefighters were called to a shed fire on Church Lane in Tooting.
A shed was destroyed by fire. part of the loft and external fascia of a terraced house adjacent to the shed were also damaged by the blaze. There were no reports of any injuries.
The Brigade's 999 Control Officers took 11 calls to the fire.
The fire is believed to have started after a stray firework ignited a wooden shed.
Station Officer James Leach, who was at the scene, said: "On arrival the shed was fully light and fire was spreading up the external side of the house and entering the eaves of the roof.
"Thermal imaging cameras were used by crews wearing breathing apparatus inside the loft of the property and by crews externally to help identify where the fire had spread to inside the house.
"An external gas pipe was damaged by the fire and we worked with partners from the Gas Authority to ensure that the supply was isolated.
"Crews worked really hard to bring the fire under control and make sure that everyone in nearby properties was safely evacuated. Around 40 people were evacuated and a 25 metre cordon was put in place as a precaution whilst firefighters worked to make the scene safe.
"We urge people to think twice before having fireworks displays or building bonfires in your garden. Despite our warning, if you do have a fireworks display always make sure fireworks are clear of any buildings, sheds, fences and hedges."
The Brigade was called at 2224 and the fire was under control by 0115. Fire crews from Tooting, Wimbledon and Mitcham fire stations attended the scene.