Oirat and Kalmyk constitute the western branch of Mongolic languages. “Oirat” is a general signifier of dialects having common features, whose speakers live scattered in a vast territory of North Eurasia (Mongolia, China, Russia, and Kyrgyzstan). Kalmyk originates from Oirat, but became a separate language in a Turkic and Russian environment in Eastern Europe. As the groups of Oirat speakers live separately in different countries and differing language environments (Khalkha, Chinese, Uyghur, Kazakh, Tibetan, Russian, and Kyrgyz), the research of its dialects is crucial for the better understanding of such linguistic strategies as the survival and revival of “typical” Oirat features in an ethnic minority position. On the other hand, the processes of change under the influence of neighboring peoples and languages can be well observed and compared. The sources for the present article are predominantly the fieldwork results from the 20th and 21st centuries (including the author’s records) and travelers’ materials from the 17th–19th centuries.