Military officers in the central province of Ha Tinh defused a 230kg (507lbs) bomb on Wednesday after it was unearthed by construction workers.
The workers discovered the bomb in the bed of a canal a day earlier.
Officer said the bomb was a highly destructive MK82 used by the U.S. during the war.
An officer said there are still several bombs from the war buried in the area.
Massive bombs left over from the war are a constant threat in central Vietnam.
Unexploded ordnance still covers a fifth of the country and explosions occur frequently, killing more than 1,500 people every year and maiming and injuring 2,200 more, according to official data.
Related news:
>Another massive war bomb found in central Vietnam
>Vietnam's never-ending war: into the trenches with the bomb disposal squad