The men, aged 35-59, filmed themselves eating a langur monkey in November and streamed the video on Facebook.
Police say the men confessed on Thursday to violating wildlife protection laws.
Vietnamese langur monkeys are one of the world's most endangered primate species, living only in the north.
"It took time for us to figure out the suspects involved," police told AFP.
In a statement, police added that one of the men bought the monkey from a hunter for 1.1 million dong (£38; $48).
Vietnam is currently home to plenty of other endangered species, including the Christmas Island frigatebird and the Siamese crocodile.
Trafficking and consumption of rare and endangered animals is a lucrative and widespread practice in the country.
Many species are used for cooking whilst others have their body parts sold for medicine.
While local and international conservation laws are in place, critics say they are not always properly enforced in Vietnam.
In 2015, authorities were criticised for selling 42 pangolins - a species of scaly ant-eater - to local restaurants after they were seized from poachers.
Le Van Minh, head of Bac Ninh's Forest Management Department in eastern Vietnam, said at the time they had dealt with the animals in accordance with the law.
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