The vessel, operated by Irish Ferries, had been in dry dock in Falmouth, Cornwall, for its annual refit and left yesterday afternoon with 113 crew on board.
The crew of the Oscar Wilde reported a fire in the engine room just before 7.30pm.
Falmouth Coastguard sent out its tug, Anglian Princess, and requested the launch of two lifeboats. Three more tugs from Falmouth docks were also launched.
A firefighting team was airlifted to the ship by helicopter.
The fire in the engine room was later suppressed by the fire systems onboard, the coastguard said.
Duty area officer James Instance said: 'The master called us as soon as he was aware of the fire, having anchored two miles south of the Falmouth pilot station.
'We were then able to put into place procedures that we have tried and tested in routine exercises with MIRG firefighting teams throughout the UK.'
The Marine Accident Investigation Branch has been informed.
There were no passengers on board the ferry and all the crew have been accounted for. No-one was injured in the incident.
The cause of the blaze is not yet known.
