Can you use american dollars in Vietnam?

You can use American dollars for sure, though in major tourist cities such as Hanoi, Hoi An and Ho Chi Minh City. When you get to Vietnam, you can change the currency to Vietnam Dong, which will help your shopping time a lot. Most shops and stores will apply very low rate when you pay in dollars so we suggest you to avoid using the dollars whenever possible.

In International airport such as Hanoi Airport or Ho Chi Minh City Airport there will be currency exchange booths for you to change the currency. Current exchange rate is 1 USD ~ 21,600 VND.