In the Western Carpathians (central Slovakia), we recorded Nyctalus leisleri in six foraging habitats. The body condition of foraging females and young varied during the season (May to August). Parturition occurred about mid-June and the first flying young were captured in the first half of July. The ectoparasites were recorded in 56.5% of examined bats and comprised seven arthropod species of mites, fleas and flies; the most common were the mites Spinturnix helvetiae (55.4%) and Steatonyssus spinosus (31.3%). Pregnant females were the most infested. Ectoparasitic flies Nycteribia latreillii and Nycteribia (Acrocholidia) vexata were recorded for the first time in this species. Seven orders of insects were found in the faecal pellets examined. By frequency (F%) and volume (V%), the major food items comprised Lepidoptera (F = 100.0, V = 55.7) and Diptera (F = 91.5, V = 25.6). The four most abundant prey categories by volume varied significantly seasonally.