A coastguard spokesman said the man, a Belarussian, was found on the left rear side of the Euroferry Olympia in apparently good condition.
The Italian-owned ferry, which was carrying more than 290 passengers and crew, as well as 153 trucks and 32 cars, caught fire three hours after it left the north-western Greek port of Igoumenitsa on Friday bound for Brindisi, Italy.
The Greek coast guard and other boats evacuated about 280 people to the nearby island of Corfu.
Eleven people remain missing.
The ship is being slowly towed to the port of Kassiopi, in Corfu, by three tugboats, authorities said.
Firefighters are still battling the blaze and thick smoke is hanging over the ship.
The extreme temperatures in some parts of the ship have impeded the rescuers from searching the whole vessel.
The ferry is slightly listing from the water poured into it to fight the fire, but authorities say it is not in danger of capsizing.
A Greek prosecutor on the island of Corfu has ordered an investigation into the cause of the fire. The Italy-based company that operates the ferry said the fire started in a hold where vehicles were parked.
The ship's captain and two engineers were arrested on Friday but were released the same day.
Passengers described a dramatic rescue situation.
One lorry driver said: "We heard the alarm. We thought it was some kind of drill. But we saw through the portholes that people were running.
"When I hit the deck, I saw smoke and children. Fortunately, they (the crew) acted quickly."
Officials said the people rescued included citizens of Albania, Turkey, Bulgaria, Romania, Greece, Italy, and Lithuania.