Four fire engines and around 25 firefighters were called to grass alight at a park in Monks Orchard Road in Beckenham.
Around eight hectares of grass and woodland was alight.
A London Fire Brigade spokesperson said: "During the hot weather we are attending a large number of grass fires across London.
"We’re asking the public to take care not to drop cigarettes or matches on dry grass and to keep a very close eye on barbecues.
"Dropped glass can also start fires as the sun can magnify the sun’s rays.
"Grass fires can quickly spread and cause serious damage, so if you see grass smouldering, please call 999 immediately.”
• Never leave camp fires or barbecues unattended and extinguish them properly after you have finished using them
• Clear away bottles, glasses and any broken glass to avoid them magnifying the sun and starting a fire
• Dispose of smoking materials such as cigarettes safely
• Explain to children the dangers of playing with and lighting fires
The Brigade was called at 1847 and the fire was under control at 2131. Fire crews from Beckenham, Woodside, Addington and Bromley fire stations attended the scene.
This incident came on the same day as crews tackled five other large grass fires across the city, with significant ones in Hornchurch, Barnet, Walthamstow, Beckton and West Wickham.