The septuagenarian is the husband of another infected British passenger who'd come in on the same flight.
The man has been quarantined and is being treated at the Hue Central Hospital in central Hue town since March 8.
So far, 14 passengers on board Vietnam Airlines flight VN54 from London to Hanoi on March 2 have tested positive for Covid-19. The flight had carried 217 passengers and crew members.
Vietnam has confirmed 49 Covid-19 infection so far, but 16 of them were discharged weeks ago. The nation had gone for 22 days without a new infection before Nguyen Hong Nhung, a 26-year old woman returning from London on flight VN54 on March 2, tested positive for the novel coronavirus on March 6.
The Covid-19 outbreak has spread to 145 countries and territories around the world, with the death toll climbing to over 5,400.