Over the past decades, sectarian conflicts in the Islamic world escalated to primary factor shaping not only international policies but also domestic politics of many Islamic countries. Likewise, scholarly interest in sectarian aspects of Islam and Islamic societies, especially in Shi’ism and Iran, is growing. As a matter of fact, rising Sunni-Shi’ite confrontation may potentially dominate the future of the Middle East, as well as of the other parts of the Islamdom. In this sectarian bipartition, the common wisdom habitually deems the Ottoman Empire and Modern Turkey within the fold of Sunni sphere. With respect to majority and state character, such an acceptance seems no wrong. Nonetheless, a significant proportion of Turkish society (like 15%), i.e. Alevis, pursue a Shi’ite oriented faith, which painstakingly situates itself outside the Sunni perimeters. In this respect, neither the Ottoman nor the Turkish population has been Sunni in its entirety. The entrance of Shi’ism into Anatolia and the Ottoman realm has not been subject of a thorough examination, albeit the question of Shi’ite beliefs in medieval Anatolia has been addressed by several scholars. On the other hand, studies on Alevi-Bektashi history and faith usually take Shi’ite elements as given. This paper aspires to investigate the penetration of Shi’ite ideals into the religious landscape of the Ottoman Empire. It argues that the infiltration of Shi’ism first in medieval Anatolia and then in the greater Ottoman realm occurred as three consecutive stages. 1) Ahl al-Bayt-centered popular Islam: As earliest sources divulge, medieval Anatolian Muslims considered themselves Sunni. However, unlike the legalist Sunnism, this was rather saturated with the love for the Ahl al-Bayt or the Prophetic Household, as well as an overstress on the event of Karbala. 2) Sufi-Alevism: The infiltration of philo-Alid beliefs in especially certain Sufi movements further escalated and assumed distinct Shi’ite tinge in the fifteenth century. This “Alevi Sufism” was distinguished with a belief in the ontological superiority of the Ahl al-Bayt, which was then considered as part of the Light of Muhammad. 3) Political and Legal Shi’ism: The last stage of “Shi’itization” was dominated by the Safavid propaganda in the sixteenth century. The Qizilbash/Alevi and Bektashi traditions emerged as a result of this three-stage “Shi’itization” process. Consulting mainly to primary sources, some of which are not published, my paper aims to delineate the landmarks of this long process.