He was an eighteen-year-old soldier in the army of the Emperor Maximian. When a public sacrifice was made to the Roman idols, Alexander refused to take part, for which he was brought before the Captain Tiberian, who told him he must either deny Christ or die. When he stood fast for Christ, he was arrested and taken through Macedonia to Byzantium, being cruelly tortured at every stop along the way. But everywhere he went, the Christians flocked to him, encouraging him and asking his blessing. His mother, Pimenia, travelled with him for the entire journey. In all his sufferings, Alexander was visited many times by an angel of God, who relieved his pain and encouraged him. As his Lord had commanded, Alexander loved and prayed for his enemies: At a place called Carasura, when the soldiers guarding him were suffering from thirst, he prayed, and a spring of cold water burst out of a dry place.
Finally, on the bank of the river Ergina, Tiberian ordered that Alexander be beheaded. As the executioner raised his sword, he saw radiant angels of God all around the holy Martyr, and was afraid to strike. Alexander asked the executioner why he had stayed his hand and, hearing the answer, prayed to God that he might send the angels away so that the executioner would not be afraid. The angels vanished, and Alexander received his crown of martyrdom. Pimenia, his mother, buried her son’s body, and many miracles of healing were worked at his grave. Some time later, Alexander appeared to his mother and told her of her approaching death, which occurred not long afterward.