f people queued for the opening of the restaurant in the southern city of Ho Chi Minh, AFP says.Ho Chi Minh, known as Saigon during the Vietnam War, was where the US-backed government was based until it fell to communist forces 38 years ago.
The restaurant is being run by the prime minister's son-in-law.
Henry Nguyen flipped burgers at a McDonald's restaurant while a teenager growing up in the United States, where his family fled at the end of the war.
He said last July, after winning the franchise, it had been his dream to open a McDonald's since returning to Vietnam more than a decade ago.
The move underlines Vietnam's hunger for Western consumer brands and the attractions for foreign investors, say observers.
Despite the Vietnamese economy's recent slowdown, foreign brands are popular among the youthful population whose parents had few of the food and lifestyle options now available in the country.
Starbucks, Subway, Burger King, and KFC all have a presence there.
Mr Nguyen is the founder of travel and food group Good Day Hospitality and managing general partner of investment firm IDG Ventures Vietnam.
He is married to the daughter of Prime Minister Nguyen Tan Dung.
