Field data on the terrestrial mammalian fauna (Eulipotyphla, Lagomorpha, Rodentia, Carnivora, Artiodactyla) of Lozen Мountain collected from 2005 untill 2019 were summarized. Several methods were used: live trapping, pitfall trapping, camera trapping, transects for signs (e.g. prints and scats), and visual observations. The investigation revealed relatively high species richness of the mammalian fauna in the area. The species composition of mammal associations in forested and open habitats, the conservation status and zoogeographic classification of the recorded species are presented. The distribution and habitat preferences of particular species (Neomys fodiens, Muscardinus avellanarius, Canis aureus, etc.) are discussed. The significance of the natural and the semi-natural habitats in Lozen Mountain for mammalian populations is considered. The main threats for the mammals and their habitats on the territory of Natura 2000 site “Lozenska planina” (BG0000165) are emphasized and recommendations for future management and monitoring activities are proposed.