Cuc Phuong is home to a huge diversity of flora and fauna. Inhabitants of the park include 97 species of mammals, most notable are the endangered langurs; 300 species of birds; 36 reptilian species; 17 species of amphibians; 11 species of fish; 2,000 species of vascular plants, and thousands of species of insects, most of whom do not bite. A number of species in the park are listed on Vietnam Red Book of endangered species.

Primates in the park include macaques, gibbon, Francois’ leaf monkey and slow loris. Other mammals including bats, porcupine, flying squirrel, small striped squirrel, belly-banded squirrel, and the rare giant black squirrel. In the past Asiatic Black-Bear bears, wild dogs, and tiger have been spotted in Cuc Phuong, but over hunting and lack of prey have jeopardized the existence of these species within the park. Leopard, clouded leopard and jungle cat may still stalk prey in Cuc Phuong.

Bird species include Bar-Backed Partridge, Scaly-Breasted Partridge, Silver Pheasant, Red Jungle Fowl, Grey Peacock-Pheasant, Laughing Thrushes, Red-Vented Barbet, Green-Eared Barbet, Scimitar-Billed Babblers, Brown Hawk Owl, Scarlet Minivet, Racket-Tailed Drongos, Racket-Tailed Magpie, White-Winged Blue Magpie. Migrant species include thrushes, flycatchers, tits, finches, pipits amongst others. Hornbills can also be spotted in the forest.

An endemic sub-species of sub-terranic cave fish is also located in the park.

Mosquitoes and leeches are present in the park, but they are not as bad as you may imagine and repellent keeps most of them away.

Flora in the park includes multi-layered canopy; trees up to 70m in height; flowers, including, orchids; ferns with amazingly tall leaves; and an abundance of lianes and cauliflory. The park also contains plants used for such practicalities as spices and medicines as well as edible fruits, nuts, and shoots.