Four fire engines and around 25 firefighters were called to reports of grass alight on Whitehall Lane in Erith.
Around two acres of shrubland were damaged by fire. There were no reports of any injuries.
A London Fire Brigade spokesperson said: “The hot weather we have been having makes the ground extremely dry, which unfortunately means grassland and parks will burn quickly when exposed to even the smallest of sparks.
“The most common causes of grass fires are discarded cigarettes. Even ones thrown from car windows can ignite dry grass verges and spread quickly. Whilst it is safer to smoke outdoors, please always make sure cigarettes are disposed of carefully, or even better yet - stop smoking altogether.”
The Brigade was called at 1528 and the fire was under control by 1704. Fire crews from Sidcup, Erith and Plumstead fire stations attended the scene.
The cause of the fire is under investigation.