Four fire engines and 21 firefighters and officers were called to a fire at a takeaway restaurant in Selsdon Road in South Croydon.
Part of the kitchen and the extraction system was damaged by fire.
One woman treated at the scene by London Ambulance Service before being taken to hospital.
The Brigade was called at 0859 and the fire was under control at 0942. Fire crews from Croydon, Woodside and Purley fire stations attended the scene.
The cause of the fire is under investigation.