A total of seventeen crew were evacuated from the 8,800-dwt Sichem Amethyst (built 2006) outside Tarragona on Saturday.
The coast guard said the blaze began in a cabin area in the accommodation block.
The captain, first officer and chief engineer remained on board to help firefighters, who eventually brought the flames under control.
The tanker was then towed into port for checks.
It had sailed from France on Thursday.
