The present study intends to shed light on the origin of the use of the episcopal mitra in the divine service of the Eastern Orthodox Church. On this subject many opinions have been issued, but most of them have not been well founded on the historical sources, or have been based on false suppositions, apparently convenient. One of these opinions, which dominated Eastern theology, is that the mitra was assumed by the Patriarch of Constantinople immediately after the fall of the Byzantine Empire, who received from the Turkish Sultan the status of ethnarch, as leader of the Christians in the Ottoman Empire. Thus, in the absence of a profane ruler, the patriarch of Constantinople began to bear the most important emblem of the Byzantine dignity, the imperial mitra, this custom being taken over in time by the other bishops of the East. The present research aimed to verify this information, to approve or disapprove some of the suppositions, and to reconstruct the context in which such an object was introduced in the Orthodox cult.