The U.S. government estimates the total population at 16.9 million (midyear 2020 estimate). According to the MCR, approximately 95 percent of the population is Buddhist, of whom 95 percent practice Theravada Buddhism. The remaining 5 percent of the population includes Christians, Muslims, animists, Baha’is, Jews, and Cao Dai adherents. Ethnic Vietnamese traditionally practice Mahayana Buddhism, although many have adopted Theravada Buddhism. Other ethnic Vietnamese practice Roman Catholicism, and these make up the vast majority of Catholics in the country. Catholics constitute 0.4 percent of the population. Nongovernmental estimates of the Protestant population, including evangelical Christians, vary but are less than 2 percent of the total population.

According to government estimates, approximately 2.1 percent of the population is Muslim, although some nongovernmental organizations (NGOs) estimate Muslims constitute 4 to 5 percent of the population. The Muslim population is predominantly ethnic Cham, although not all Cham are Muslim. The Cham typically live in towns and rural fishing villages on the banks of the Tonle Sap Lake and the Mekong River, as well as in Kampot Province. There are four main Islamic traditions represented in the country. Nearly 90 percent of Muslims are adherents to Sunni Islam, subscribing to the Shafi’i school of Islamic law. The remaining minority practice Salafist, Wahhabist, and Ahmadi doctrines. A portion of the Cham community also subscribes to the indigenous Iman-San sect of Islam, combining traditional ancestral practices with Sunni Islam.

An estimated 0.28 percent of the population is ethnic Phnong, the majority of whom follow animistic religious practices. An additional estimated 0.25 percent of the population includes Baha’is, Jews, and Cao Dai adherents.