The rise of the Safavids to power was marked by their implementation of Shi'ism as the official religion of Iran, a move that played a vital role in solidifying their legitimacy. On the other hand, the Sunni Ottomans, who adhered to the Hanafi school of thought, established their dominance over the Islamic world. The conflicting religious beliefs and competing claims to leadership had significant consequences for the policies of both states, leading to long-lasting tensions that lasted for centuries. They made no effective attempts to resolve the sectarian and religious conflicts among themselves. The ascension of Nader Shah Afshar in Iran brought about a significant shift away from the Safavid tradition. Through his initiatives, he successfully established the Jaʿfari denomination, which played a crucial role in promoting harmony between Shia and Sunni communities. Later, he suggested to the Ottoman Empire that they formally acknowledge it as the fourth orthodox Islamic denomination. However, the Ottomans did not confirm it . Finally, Nader convened a meeting of ulama from all Islamic world in Ecumenical Islamic Council of Najaf (1743). After several days of debate on the question of the Jaʿfari denomination, the participants signed a document, which recognized the Jaʿfari denomination as a legitimate legal school of Sunni Islam. However, the outcome did not impress the Ottoman sultan. Despite the considerable efforts exerted by Nader Shah and the establishment of the Ecumenical Islamic Council of Najaf, his plan ultimately failed. The primary objective of the current research is to address the question of why the Ecumenical Islamic Council of Najaf did not achieve practical success in the end. In order to effectively tackle this question, it is essential to thoroughly examine the important approaches taken by the Ecumenical Islamic Council of Najaf. At the Ecumenical Islamic Council of Najaf, we encountered five different approaches, which can be divided into two scholarly approaches represented by Suveydi, an Ottoman scholar, and Molabashi, Nader Shah’s scholar, as well as three state approaches represented by the Ottomans, Iraq’s governor, and Nader Shah. Each of them had their own interests, motivations, and objectives. To initiate this study, the initial step entails gathering the necessary information from chronicles, direct correspondences, and the Council’s report. After carefully examining the compiled information, the aforementioned approaches will be assessed, leading to a comprehensive conclusion.