The Park is potentially rich in faunal resources and contained about 78% of the primate species recorded in Nigeria, many of which are endemic. Notable among these are the critically enda, Pan troglogytes and Cercopithecus sclateri (an endemic species). The Cross River gorilla is significant as the only colony of gorillas in the whole of sub-Saharan Africa. The Nigerian Government, in active collaboration with its Cameroonian counterpart, is assiduously working together to ensure the protection and survival of the highly endangered Gorilla species.
In addition, the Park also harbors about 30 species of other non primate mammals including the African forest elephant, Loxodota africana cyclotis; Hippopotamus, Hipopotamus amphibious; Forest buffalo, syncerus cafer nanu;, Giant otter shrew, Potomagale veloxl and a new species of shrew.
Bird life is also very rich. About 30% of Nigeria 860 species of birds are found in the Park. These include the endangered Red headed rock Picathartes oreas, the rare Green ibis Bostrychia olivacea, the violet-backed fly catcher, Hyloita violacea and the black guinea fowl Agalacea niger etc. Other endemic avifaunas include Bannerman’s waever, White throated babler and Green breasted bust strike.-questionable bird names
Over 90 species of butterflies representing 30% of all African butterflies have been identified, four of which are endemic to the Park while two, Tetrahanis okwangwo and Tetrahanis oboti are new to science. Also recently documented in Oban Division are two new species of frogs Didynamipus sjooesteati and Nyctibates corrugatus that are new records in Nigeria.
Animal sighting in high rainforest ecosystem such as the Cross River National Park is very rare, despite species diversity, due to low visibility.
The Park, being part of the Guinea-congolian region is characterized by high floral species richness and endemism: 1546 species of plants from 523 genera in 98 families have been recorded. Six are new record for Nigeria and four are new to science. The new records are Asplenium cornotum, Arthropteris monocarp, Bulbophyllum bequaertii, Bulbophyllum odicum, Disperia nitida and Haeneria obovata. Trydactile spp., Uapaca spp., Habeneria spp., and Afrocalathea flavida are new to science. Two species; Anceistocladus korupensis and Prunus africana have generated global interest because they are reputed to have properties which may be effective against HIV/AIDS and prostate cancer respectively.