The plans to establish a Turkish-Armenian Catholicosate in the 17th century are central to understanding the issues relevant to Armenian history in that era. The authority of the Catholicosate at Etchmiadzin extended over almost all the Armenian realms, which were spread mainly within the territories ruled by the Ottoman Empire and Iran. In these empires, Armenians lived in religious community units and had internal autonomy. The Church exercised the functions entrusted to it through both the officials it appointed and those it sent on missions to the territories. The supremacy of Etchmiadzin, however, began to come under question and faced resistance. The existence of two state systems—the Ottoman and Iranian—ran counter to the system of management from a single center. The separatists had no deep ideological contradictions against the Armenian Church and did not reject its doctrine, but they had economic and political reasons to break away from the authority of Etchmiadzin. The sides also managed to involve representatives of the ruling elite in this struggle, urging them to view the Armenian issue in the context of Ottoman-Iranian opposition. The struggle led to the formation of conflicting parties that identified themselves through the names that the two Armenian populations—the Eastern Armenians and Western Armenians—gave each other, respectively Ajem (“Iranian”) and Tajik (Ottoman). The historiographical writing of this period not only outlines this political division, but also becomes a platform to preach the interests involved in this conflict, with the historian assuming the role of someone promoting the interests of one party or the other. In addition to the historiographical text commissioned by the parties, the preserved sources include numerous letters, archive materials, manuscripts and printed book references, a comprehensive examination of which will expose the core of the conflict between the Eastern and Western Armenians. Later, Etchmiadzin restored the status of the Mother See, and also reestablished its monopoly over a significant portion of the historiographical texts, describing the anti-Etchmiadzin movement in an extremely negative light. These assessments have also become dominant in historiography in general, which in turn has attempted to promote the legend of Armenian unity and to characterize Turkish-Armenian separatism as a national calamity. This study aims to address the issue of anti-See Catholicosates, which has been pushed by mainstream history to the margins, and to examine the impact of the Ottoman and Iranian political configurations on 17th-century Armenian political and economic history.