Diomedes was born in Tarsus. He was a physician by profession and a zealous Christian evangelist. He traveled a good deal preaching the faith. When he arrived at Nicaea, Diocletian ordered him arrested. On route to Nicomedia, Diomedes paused to pray and then died. The soldiers took his head as proof he had been arrested.[2] One source states, "It is said that when his head was taken to the emperor, that all were blinded, and only after his body has been returned and they had prayed, was their sight restored."[3]
There is another Saint Diomedes who is celebrated on 2 September. With Julian, Philip, Theodore, Eutychian (Eutykhian), Hesychius (Heyschios), Leonides, Philadelphus (Philadelphos), Menalippus (Melanippos), and Pantagapes (Parthagapa) he was martyred at an unknown date and site. They suffered various forms of execution (burning at the stake, drowning, beheading, or crucifixion).