He was a renowned commander in the Imperial army, and dwelt in Heraclea of Pontus. The Emperor Licinius heard of Theodore's fame as an officer, and also that he was a devout Christian; the Emperor determined to visit the general, officially to honor him, but secretly to turn him from Christ.

When the Emperor came to Heraclea, Saint Theodore met him with all honor, and the Emperor in turn praised him for his service to the state. Licinius then publicly bade Theodore make sacrifice to the gods. Theodore asked that he be given the most venerable gods, made of gold and silver, to attend upon at home, and promised that the following day he would return and honor them before the people. The Emperor, thinking that he had succeeded in restoring Theodore to paganism, gladly agreed.

That night the Saint smashed all the idols he had taken home, and distributed the gold and silver pieces to the poor. When this was discovered, Theodore gladly admitted his deed and confessed Christ boldly. The Emperor, in a fury, had the Saint subjected to many tortures, then crucified. On the cross, he was subject to further torments and mutilations: parts of his body were cut off, his eyes put out, and he was shot with arrows, finally being left on the cross for dead. The next day Licinius sent men to cast his body into the sea, but to their amazement they found the Saint alive, his body perfectly intact. Through this, many spectators and some of the Emperor's own men turned to Christ. Seeing that the Saint, far from renouncing Christ, was leading others to Him, the Emperor promptly had him beheaded. His holy relics were returned to his family home in Euchaita, where they worked so many miracles that the town came to be known as Theodoropolis.