Four fire engines were sent to Amberley Castle in Arundel, West Sussex, just after midnight, the fire service said.
A spokesman said: “Firefighters dealt with a fire in a room. All guests were safely evacuated to the village hall where they were looked after by fire service and hotel staff before they could be found other hotels for the night.
“The fire had spread to the roof space above the room. Four breathing apparatus were used with four appliances and one aerial ladder platform.
“The fire was put out and salvage operations took place to protect the remaining historic property.
“Fire crews remained throughout the night to ensure the safety of the hotel. A fire investigation will take place later this morning”
John Badley, regional general manager, added: “Following a small fire at Amberley Castle in the early hours of March 1, all of our guests and staff were safely evacuated and accounted for, with no injuries reported. We are most grateful for the prompt actions of both the fire service and our hotel colleagues who aided the safe evacuation of all guests.”