The fire on the Admiral Kuznetsov broke out during welding work at a shipyard in the Arctic port of Murmansk and spread quickly through the carrier's internal compartments. Emergency crews spent the day battling the blaze.
Authorities in Murmansk said 11 people were injured and 10 of them were hospitalized in intensive care units.
The Admiral Kuznetsov has been plagued by breakdowns and setbacks since its launch in 1985. The massive blaze follows a 70-ton crane crashing onto the Admiral Kuznetsov's deck in October 2018 when a mammoth floating dock holding the ship sank.
The crane left a hole of 20 square meters (215 square feet), and the loss of the dock significantly slowed down repairs on the carrier since the navy lacked another of comparable size.
Thursday's fire will further push back the work to fit the ship with modern control systems and new weapons.
With its turbines belching black smoke, the Admiral Kuznetsov looks outdated compared with the nuclear-powered carriers of the United States. However, the Kremlin has used it to project military might far from Russia's shores.
Two years ago, the Admiral Kuznetsov was deployed to the eastern Mediterranean as part of Russia's campaign in Syria, launching the first carrier-mounted attacks in Russian naval history.
It lost two carrier-borne fighters in incidents during the Syria mission.