Unlike the majority of Mongolian scholarship, this work examines the history of Buddhism among Mongolian ethnic groups. Numerous works exist on the Oirats and their history, but most of the research has been devoted to the study of Buddhism in the Mongolian empire during its formative years. The Oirats were the Western Mongolian people who made significant impact on the history of Central Asian people for a period of several centuries. Entering onto the historic scene under the leadership of Genghis Khan, the Oirats, fighting for their own independence, were constantly engaged in wars against the Mongols, Chinese and Turkic people. In the middle of the fifteenth century the Oirats managed to unite the whole of the Mongolian world under their rule while, two centuries later, they formed three separate states: that of Dzungarian state in Central Asia, Khoshout state in northern Tibet, and the Kalmyk (Torgout) state near the Caspian Sea in Russia. Interest in the Oirats and their history has been quite considerable and a number of issues have been highlighted, both in Russian and foreign historiography. It should be noted, however, that the pre-Dzungarian period of Oirat history (i.e. up to the middle of the seventeenth century) has been the least investigated area in historical scholarship. It was also then that the Oirats finally came to their Buddhist outlook and Buddhist culture (a local example of Buddhist civilization) as part of their socio-political development. Buddhism as a systemic religion fundamentally differed from the primitive cults of their earlier society and was much more in line with the social changes taking place at the time and thus succeeded in replacing the old beliefs of the Oirats. The Buddhist tradition of the Oirats of the early Middle Ages is indissolubly connected with its further development among the Oirats (the Kalmyks) of the late Middle Ages. The examination of this Buddhist tradition, in its early stages being appropriated by the Oirats as their dominant worldview, allows a greater degree of certainty in answering numerous questions as far as the study of the history and culture of the Oirats and Kalmyks of later periods.