The 29,213-DWT car carrier Courage was reported to have caught fire some 75 miles north of London.
The blaze was successfully extinguished by the crew who were using the onboard CO2 system.
A helicopter was dispatched to monitor the situation and a team of firefighters were winched aboard to assess the vessel.
The owner of Courage, American Roll-On Roll-Off Carriers, commented for BBC:
"A fire started on board and was put out by the ship's crew. We don't know how much damage has been done to the ship or the cargo.”
There were no reports of injuries or pollution released. The car carrier arrived in Southampton today at 05:04 UTC.