Fifteen fire engines were dispatched after the alert was raised.
“The main aim is to stop the fire from spreading,” a fire service spokesman said this morning.
About 150 workers have been evacuated. There is no casualty said fire service spokesman Yvon Bot but a large part of the building is affected.
The cause of the blaze is under investigation.
The four-storey classically styled hotel in Place Vendôme in central Paris has been closed for renovations works since 2012 and was due to re-open in March.
Several of its suites are named in honour of famous guests of the hotel, including Coco Chanel and Ernest Hemingway who lived at the hotel for years.
It is currently owned by Egyptian billionaire Mohamed Al-Fayed.
The hotel opened its doors on 1 June 1898.