Le Trong Tuong, 45, Cao Minh Luan, 47, Tran Cong Trang, 33, and his brother Tran Cong Hung, 30, face charges of "violating regulations on endangered and rare animals."
Hung is in police custody while Tuong, Luan, and Trang are under house arrest.
According to the Huong Son District police, on November 29 they flagged down Hung's car and found a serow weighing 60 kilograms inside. He could not provide any documentation to show its origin, and said he was carrying it for Trang.
Summoned by the police, Tuong and Luan said they trapped the animal in a forest and sold it to Trang for a few million dong. (VND1 million = $43)
The police are investigating Trang's purpose of buying the animal.
In Ha Tinh, many people illegally buy wild animals like tigers, serows and monkeys for using their body parts to make bone glue as traditional medicine, believed to be beneficial to health.
They are lucrative for the makers, with 100 grams of serow products fetching VND20 million and tiger products, VND18 million.
Serow, scientific name Capricornis milneedwardsii, is listed by the International Union for Conservation of Nature as endangered, and is banned from use in commercial trade.