East Sussex Fire and Rescue Service was called to Windlesham Manor on Hurtis Hill in Crowborough in the early hours of this morning.
The alarm was raised at 00.44 with reports there was smoke in a room in the building.
Three fire engines were sent from Crowborough and Uckfield.
Six firefighters wearing breathing apparatus went into the building.
Crews used two hose reel, firefighting foam, a thermal imaging camera and a PPV fan to clear the smoke.
One person was taken to hospital suffering from smoke inhalation. A number of other people were checked over by South East Coast Ambulance crews.
It is believed to be an accidental electrical fire in the roof space.