The paper presents some research results on origins and early history of the Old Bargut people and the New Bargut people, under-researched Mongol-speaking ethnic groups living in Northeast China (Hulunbuir prefecture). Source data unanimously show that both groups originally come from the eastern coast of Lake Baikal, which prior to the XVI century was considered to be the historic centre of the vast Bargugin-Tokum area. Analysis of the original name of the Old Barguts (Barga) leaves no doubt that they are the descendants of the community Bargut, which is known for the participation in Mongolian events in the XIII century, and whose ethnogenesis goes back to baegu, one of the main groups in the Turkic-Teles union. The New Barguts are a part of the Bagugin-Tokum tribe Khori, who, after establishing the Russian-Chinese border in 1727, could not return to their homeland. The change of ethnic self-identification resulted in a loss of the connection with the original ethnic group, and the New Barguts started to identify themselves as an independent ethnic unity. The studies of the Bargut history have been particularly focused on the social organisation of the foreseeable past of the Old Barguts. The particularity of the interrelation between the Old Bargut clans, their exogamy at the clan level, and endogamy at the ethnic group level strongly indicate that the Old Barguts by the time of their arrival to Northeast China were a tribal group that was archetypally organised by dual phratry principle.