The origin of Dorotheos is unclear, nor is anything about his early life known except that prior to his appointment to the see of Trebizond in 1472, he was Metropolitan of Athens as mentioned in his act of election to Trebizond. His activity in Athens is equally unknown, however, nor is he mentioned by any historians of the region. Dorotheos was appointed to Trebizond in succession to Pankratios, who had only months before been appointed metropolitan after a vacancy dating back to the capture of Trebizond by the Ottomans in 1461.