The three men, aged 33-34, landed at Van Don International Airport in northern Quang Ninh Province on July 3. They were admitted to Hanoi's National Hospital for Tropical Diseases on July 5.
Eleven others on the same flight were also confirmed infected.
The three had tested negative for the novel coronavirus twice before they were announced recovered.
The National Hospital for Tropical Diseases is the capital’s frontline facility for treating Covid-19, having cured 187 patients so far.
Vietnam has recorded 383 Covid-19 cases to date, of whom 360 have been announced recovered. The country has recorded no community transmission in over three months.