A total of 1231 species of invertebrates have been identified in the park, and the level of research has been identified as low given the overall richness of the groups, favorable conditions, diverse habitats and the lack of targeted research. The endemic species a total of 58 species, of which 28 Balkan and 18 species are local endemics. The main reason for the large number of endemics is the presence of rich underground fauna. The endemic complex of species gives a high degree of uniqueness to the fauna in Vratsa Mountain.
More than 500 caves and precipices have been discovered and studied on the territory of the Vratsa Balkan Nature Park, which are unique with their cave fauna. Of all the cave species found here: 17 are indicators, 37 are Bulgarian endemics, 28 are Balkan endemics, 36 are rare and 9 are North Aegean and Paleo-Aegean relics. Of great zoogeographical importance is the fact that Vratsa Mountain is the evolutionary center of the endemic genus Pheggomizetes (light-hate beetles).
Due to the great species diversity, the high level of local and regional endemism, as well as the strong vulnerability to anthropogenic interference, the protection of cave invertebrate fauna in the reserve and the park is generally extremely important.
Vratsa Balkan Nature Park is one of the important regions for butterflies in Bulgaria.