The male patient, 53, lives in Hanoi capital. He was among Vietnamese citizens boarding flight VN5062 from Russia to Vietnam on July 9.
He was transferred to a concentrated quarantine facility in Ca Mau province upon arriving at Can Tho International Airport in the south. He tested positive for the virus on July 12.
The patient was admitted to the Ca Mau Provincial General Hospital for medical observation and treatment.
According to the Ministry of Health, Vietnam has gone through 89 days without locally transmitted coronavirus infections.
The country has so far recorded a total of 373 COVID-19 cases, of which 352 cases have fully recovered, making up 94.4%. Of the 21 remaining cases, 6 patients have tested negative for the virus at least once. No deaths have been reported.