Much like Hinduism, adherence to Islam in Vietnam is primarily associated with the Cham ethnic minority, although there is also a Muslim population of mixed ethnic origins, also known as Cham, or Cham Muslims, in the southwest (Mekong Delta) of the country. Islam is assumed to have come to Vietnam much after its arrival in China during the Tang Dynasty (618–907), through contact with Arab traders. The number of followers began to increase as contacts with Sultanate of Malacca broadened in the wake of the 1471 collapse of the Champa Kingdom, but Islam would not become widespread among the Cham until the mid-17th century. In the mid-19th century, many Muslims Chams emigrated from Cambodia and settled in the Mekong River Delta region, further bolstering the presence of Islam in Vietnam.
Vietnam's Muslims remained relatively isolated from the mainstream of world Islam, and their isolation, combined with the lack of religious schools, caused the practice of Islam in Vietnam to become syncretic.
Although the Chams follow a localised adaptation of Islamic theology, they consider themselves Muslims.
However, they pray only on Fridays and celebrate Ramadan for only three days. Circumcision is performed not physically, but symbolically, with a religious leader making the gestures of circumcision with a wooden toy knife.
Vietnam's largest mosque was opened in January 2006 in Xuan Loc, Dong Nai Province; its construction was partially funded by donations from Saudi Arabia.
A 2005 census counted over 66,000 Muslims in Vietnam, up from 63,000 in 1999. Over 77% lived in the Southeast Region, with 34% in Ninh Thuan Province, 24% in Binh Thuan Province, and 9% in Ho Chi Minh City; another 22% lived in the Mekong River Delta region, primarily in An Giang Province. In Ninh Thuan Province, where most of the Cham in Vietnam reside, Cham Bani (Muslim Cham) number close to 22,000. Out of the 22 villages in Ninh Thuan, 7 are Muslim.