Authorities in Xuan Truong-Dalat Ward, Lam Dong Province, said they were helping recover the vehicle after the incident at Xuan Thanh Stream.
Heavy rain earlier in the day sent water surging downstream, creating strong currents in the stream.
Nguyen Thanh Chau was driving the truck across the spillway when it was suddenly swept away. The vehicle was carried several metres downstream before overturning on its side.
Chau and two others in the cab managed to escape and reach the bank safely.
Local authorities arrived at the scene to assist with recovery efforts.
Residents said the spillway is commonly used for local travel and transporting goods. It is easily passable in dry weather but becomes dangerous during heavy rain because of strong currents.