The blaze started on the deck of the vessel St Faith during the 09:00 GMT sailing from Portsmouth to Fishbourne on the Isle of Wight.
The firm said the fire, in a "non-passenger area", was extinguished by the crew within minutes and none of the 65 people onboard were injured.
Ferry services have returned to normal.
The St Faith has been taken out of service while an inquiry takes place.
A lorry driver who was on board said: "I could smell the smoke, the stewards moved us downstairs, but there was no panic.
"There was quite a jolt as the ferry docked and there were fire engines waiting."
Wightlink said emergency services met the vessel "as a precaution" when it docked on the island and passengers and vehicles disembarked as usual.
There were 52 passengers and 13 crew onboard.
Operations director Elwyn Dop said early indications showed the fire may have started in an air conditioning unit close to the bridge.
"We had 13 crew members dealing with the incident.  They are well exercised in their duties and they used those skills to deal with the situation today. The passengers were looked after calmly in the lounge," he said.
A fire that broke out on a car ferry as it crossed the Solent may have started in an air conditioning unit, operator Wightlink has said.