Turkish intelligence agents captured Nazik in Syria in September and brought him to Turkey. He was accused of planning and organizing two car bombings that killed 52 people in the town of Reyhanli, near the border with Syria.
Turkey blamed Damascus for being behind the explosions, saying they were carried out by a Turkish Marxist group with alleged links to Syria's intelligence agency. The Syrian government has denied the accusations.
Two other suspects were sentenced for aiding a terror group.