Four fire engines and around 25 firefighters tackled a fire at a hospital on London Road in Thornton Heath.
A room inside the hospital was destroyed by fire. There were no reports of any injuries. Around 80 to 100 people left the building before firefighters arrived.
The Brigade received five calls about the fire.
The Brigade was called at 1458 and the fire was under control by 1708. Crews from Croydon, Norbury, and Wallington fire stations attended the scene.