Anthropologically, the Mongols are quite homogeneous, belonging to the classic physical type to which they lent their name. Within Mongolia, Khalkha-speaking Mongols constitute almost four-fifths of the population. Other Mongolian groups—including Dörbed, Buryat, Bayad, and Dariganga—account for about one-eighth of the population. By tradition the Mongols have been Buddhists. Much of the rest of the population consists of Turkic-speaking peoples, mainly Kazaks, who traditionally have been Muslims; located mainly in the western part of the country, they have been granted an autonomous area. A small but significant number of Russians live mainly in the cities. The Chinese, who were formerly important in cities, trade, and finance, have largely left the country.

At the time of the founding of the modern state, the social composition was strongly influenced by the then-prevailing religious traditions of the lamas (monks), who followed tenets derived from Tibetan Buddhism, with a strong admixture of more primitive elements. Control lay in the hands of the head of the Mongolian Tibetan Buddhist Church (who was proclaimed the khan of all Mongolia) together with various local khans, hundreds of princes and noblemen, and the higher clergy. The new regime sought to replace feudal and religious structures with socialist and secular forms. During the 1930s the government closed monasteries, confiscated their livestock and landholdings, induced large numbers of monks to renounce religious life, and eliminated others. The number of Buddhist monks dropped from 100,000 in 1924 to 110 in 1990. Many aspects of the national cultural traditions are preserved in museums.