The Circassians, who had been mostly ignored by the empires surrounding their lands, entered the orbit of the Ottoman Porte in 1556 with the annexation of Astrakhan by the Tsardom of Muscovy and became a contested borderland between the Ottomans and Muscovites. This paper will analyze the Ottoman methods of Islamization of the Circassians of the North Caucasus in the 17th century. Ottoman documents demonstrate that starting in the second half of the 16th century, the Ottoman Porte made a concerted effort to convert the animist Circassians to Islam in the expectation that conversion would cement their loyalty or allegiance to the sultan. It is well known that the Circassians, especially their rulers, could convert to Islam or Christianity depending on their political alliances. For Circassian rulers, however, converting to or following a certain religion did not necessarily translate into allying with or submitting to the imperial power professing the same religion. Most of the time rulers were very open to conversion and there are examples of rulers and nobles who converted to a different religion more than once or of families with Christian, Muslim, and animist members. Although we know about conversions of Circassian rulers, it is more difficult to understand how conversion happened at the people’s level. In investigating the conversion of the commoners in the Circassian lands, this paper will utilize Ottoman and Russian archival documents, travelers’ accounts, chronicles, and other narrative sources. Islamization of the Circassians peoples of the North Caucasus occurred between the 16th and the 19th centuries. Apart from political alliances and missionaries sent by the Ottoman Porte and Crimean khans, places of pilgrimage, which in the North Caucasus also served as places of commercial fairs, facilitated the religious transfer owing to the abundance of merchants from the Islamic lands. These merchants not only traded in goods but also, in a clear parallel to many other frontier regions of the Islamic world, consciously encouraged a synthesis of Islam with local beliefs and, ultimately, conversion. This paper will present a model of such a merchant-facilitated conversion as it developed in the specific conditions of the Circassian tribal societies in the 17th-century North Caucasus. Special attention will be paid to the contribution of pre-existing places of pilgrimage and commercial fairs to initial religious synthesis that eventually led to mass conversions of animist Circassians to Islam.