According to the official logbook, the ivory was found by customs in the northern port of Haiphong in a container supposedly carrying peanuts.
Photos released by the customs department showed hundreds of long ivory tusks stacked in front of an open container.
The shipment was sent to Vietnam via Singapore, authorities said.
Tusks and other elephant body parts are used as talismans and in traditional medicine in some parts of Asia, although there is no scientific evidence of such medicinal properties.
Vietnam officially banned the ivory trade in 1992, but the country remains a hub for illegal wildlife transport in Asia.
More than 60 tonnes of ivory, pangolin scales and rhino horns have been seized at Vietnamese seaports since 2018, according to a 2021 report by Education for Nature Vietnam, a non-governmental wildlife protection organization.
With information from Lusa