The 29-year-old patient, who lives in Ho Chi Minh City, had been left stranded in China following his trip to the mainland since Mid-January 2020.
He boarded a plane from Hubei (China) to Nanning (China) on May 31, and then returned to Vietnam through the Mong Cai international border gate in Quang Ninh province.
The man was immediately transferred to a concentrated quarantine centre in Mong Cai for medical observation according to regulations.
He first tested negative for the virus on June 3, but the second test came back positive on June 11.
The patient was then admitted to the Hospital of Tropical Diseases No2 in Hanoi for monitoring and treatment.
As of 6pm on June 13, Vietnam has reported 334 coronavirus cases and no deaths. As many as 323 patients have fully recovered from the virus, making up 96.7% of the total confirmed cases.
The remaining 11 cases are receiving treatment at 6 hospitals, with most of them in stable health condition. Four of them have tested negative for the virus at least once.
According to the Ministry of Health, Vietnam has gone 58 days in a row without new locally transmitted infections. About 194 people returning from epidemic hit countries were quarantined as soon as they landed in Vietnam posing no risk to the community.