Police in the central province of Thanh Hoa found 2.7 tonnes of tusks inside cartons on the back of a truck that was on its way to Hanoi, according to a report on their website.
"This is the largest seizure of smuggled ivory ever in Thanh Hoa province," the report said.
State media said the elephant tusks originated from South Africa.
The truck driver claimed he was unaware of what he was transporting, according to a report in state-controlled Tuoi Tre newspaper.
Police declined to comment further when contacted by AFP on Sunday.
The global trade in elephant ivory, with rare exceptions, has been outlawed since 1989 after populations of the African giants dropped from millions in the mid-20th century to around 600,000 by the end of the 1980s.
There are now believed to be some 415,000, with 30,000 illegally killed each year.
Prices for a kilogramme (2.2 pounds) of ivory can reach as high as $1,100.
Vietnam outlawed the ivory trade in 1992 but the country remains a top market for ivory products prized locally for decorative purposes, or in traditional medicine despite having no proven medicinal qualities.
Weak law enforcement in the communist country has allowed a black market to flourish, and Vietnam is also a busy thoroughfare for tusks trafficked from Africa destined for other parts of Asia, mainly China.
Last October, Vietnam customs authorities discovered about 3.5 tonnes of elephant tusks at Cat Lai port in Ho Chi Minh city, all in crates of wood, including a hefty two-tonne haul packed into a single shipment.
In 2015, 2.2 tonnes of tusks, originating from Mozambique, were discovered and seized northern Hai Phong port.
And last week authorities in Hong Kong seized 7.2 tonnes of ivory, the largest haul in the city for three decades.
While low level couriers are sometimes arrested across Asia very few wildlife trafficking kingpins are brought to justice.
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