Four fire engines and around 25 firefighters tackled a fire at a hospital block under refurbishment on Frognal Avenue in Sidcup.
A storage room was destroyed by the fire. There were no reports of any injuries.
Control Officers took the first of three calls at 0342 and mobilised crews from Sidcup, Eltham, Orpington and surrounding fire stations to the scene. The fire was extinguished by 0528.
The cause of the fire is under investigation.