There were no immediate reports of injuries, a coast guard official told Reuters.
The Eleftherios Venizelos, carrying 875 passengers and 141 crew, was sailing off the island of Hydra when it notified the coast guard around midnight (2100 GMT) that a car parking compartment had caught fire.
The ferry has docked in Piraeus and passengers are leaving the vessel, the official said.
A Reuters witness saw passengers in lifejackets walking down a sideway stair, while fumes were still coming out of the ship. Firefighters were deployed at the pier.
