Haiphong police said on Monday that Lai Khe Commune Police received the monkey after the resident voluntarily reported and surrendered the animal.
The man discovered the monkey in his garden and contacted local police, who worked with the commune authorities and forest rangers to identify it as a Group IIB protected species under Vietnam's wildlife protection regulations.
The monkey was later transferred to the relevant authorities for care before being released into its natural habitat.
Police said the red-shanked monkey is listed in Vietnam's Red Book of threatened species and praised the resident's actions as a contribution to wildlife conservation, biodiversity protection and public awareness of wildlife protection laws.