Road construction workers in the central province of Quang Tri found a bomb of around 270 kilograms (615 lbs) on Wednesday.
The bomb, 1.7 meters long, was found two meters underground.
Authorities said the bomb is an unguided, general-purpose Mark 82 used by the U.S. during the Vietnam War.
Members of the U.S.-based bomb removal organization PeaceTrees Vietnam have moved the bomb to a safe place for detonation.
Quang Tri was the hardest hit by bombings during the war. The province was a center for American military bases and a principle battleground during the 1968 Tet Offensive.
An estimated 400,000 pieces of unexploded ordinance, or UXO, remain buried across 480,000 hectares (1.2 million acres) of land in Quang Tri. They can be found in residential areas, gardens and even under houses.
Across Vietnam, UXO still threatens a fifth of land mass and explosions occur frequently, killing more than 1,500 people every year and maiming and injuring 2,200 more, according to official data.