Customs officials in Hai Phong found tons of pangolin scales smuggled to the northern port city in a container labeled as seaweed on Wednesday.
Quang Minh, Ltd. from nearby Lang Son Province had imported the container and was going to export it to the third country.
Customs officials and environment police found small bags of pangolin scales inside the large bags containing seaweed.
It was not immediately clear where the scales had come from or where they were going, investigators said.
The pangolin is listed in Vietnam's Red Book as endangered and the animal is protected by laws that forbid the trade of its parts.
China's demand for pangolin scales for medicinal use is threatening the survival of the vital pest eaters in Southeast Asia, wildlife trade monitoring group TRAFFIC said in a report last year.
"Pangolins save us millions of dollars a year in pest destruction," Simon Stuart, who chairs the Species Survival Commission of the International Union for Conservation of Nature, was quoted by AFP in a report last year.
Hai Phong customs on Wednesday last week found nearly two tons of elephant tusks in a container smuggled on a Hong Kong boat. The container was also labeled as containing seaweed.