Police and customs officers in Da Nang on Friday seized more than two metric tons of elephant tusks inside a timber container from Nigeria.
Officers said the tusks were hidden in many bags buried deep under more than a thousand wood logs.
The shipment arrived at Tien Sa Port in the central city on August 11.
Vietnam has banned ivory trade since the 1990s, and yet it has been fueled by the rising affluence in recent years and the demand for using ivories for decoration.
Officers said the tusks can sell for around VND100 billion (US$4.44 million) on the black market.
The invoice named a local business as the receiver of the shipment.
The company was earlier named as the recipient of a Mozambique shipment which was seized by Da Nang customs on August 13 for containing nearly 750 kilograms of elephant tusks and rhino horns.
Both products are strictly banned from commercial use worldwide to protect the endangered animals.
The company has denied responsibility.