Numerous invertebrates are endemic or relics: 28 species of aquatic worms, 12 species of Lumbricidae, of which Allolobophora carpatica is an endemic species for Rodnei and Maramureș Mountains. Many species of Collembola have been identified, but the most important one is Tetrachanthella transylvanica. Diplopoda are represented by 20 species, of which 9 are endemic species, such as: Glomeris promineus, Polydesmus daday. As for Chilopoda, 36 species have been identified, of which 6 species are endemic, such as: Clinopodes rodnensis, Lithobius matici. Orthoptera are represented by 39 species, of which Isophia brevipennis, Pholidoptera transylvanica and Miramella ebneri carpathica are endemic species.
Lepidoptera are represented by more than 295 species, some of them being internationally protected: Erebia pharte carpatica, Erebia epiphron transylvanica, Erebia sudetica etc. Numerous vertebrates can be found in this park, many of them being characteristic for Eastern Carpathians. Rivers stand for the appropiate habitat for many species of fish, such as: brown trout (Salmo trutta fario), grayling (Thymallus thymallus) and minnow (Phoxinus proxinus). As for reptiles, worth mentioning is a relic species, the common lizard (Lacerta vivipara), which has been pinpointed in specific habitats, while the most representative birds are the black grouse (Tatrao tetrix), which breeds just in north-Romanian mountains, capercaillie (Tetrao urogallus), and golden eagle (Aquila chrysaetos).
Some representative mammals can be found, such as: chamois (Rupicapra rupicapra), alpine marmot (Marmota marmota - introduced in this area), red deer (Cervus elaphus), roe deer (Capreolus capreolus), wild bore (Sus scrofa), brown bear (Ursus arctos), wolf (Canis lupus), lynx (Lynx lynx) and pine marten (Martes martes).