Customs officials allege textiles, fisheries, farm products, tiles, honey, iron, steel and plywood are among the Chinese products that are most often being relabelled and then exported to a third country.
Vietnam's government has said the country's customs department is now going to be more aggressive in checking certificates that state products' origins.
In one case, US customs officials found a shipment of Chinese plywood that had been relabelled to make it appear it originated in Vietnam.
Foreign Minister Pham Binh Minh has warned of serious consequences if such actions cannot be controlled.
"It will sabotage Vietnamese brands and products and it will also affect consumers," he said.
"We could even get tariff retribution from other countries, and if that happens, it will hurt our economy."
The US is Vietnam's largest export market, while it imports the most from China.
In a spiralling trade war, the US is imposing 25% tariffs on $250bn (£196bn) in Chinese goods.
Beijing has hit back by targeting $110bn (£86bn) worth of American products.