Depredation by wolves (Canis lupus) could threaten survival of reintroduced wild Przewalski horses (Equus ferus przewalskii) in Hustai National Park (HNP), Mongolia. We conducted scat analysis, spatial analyses of kills, and interviews to study prey species selection and temporal and spatial factors that characterize prey choices of wolves. Diet of wolves in HNP was comprised of >50% of livestock. Diet composition varied during the year, with more livestock taken in winter. Wildlife species were selected over livestock species. From available livestock species domestic horses were predated most, whereas red deer (Cervus elaphus) and marmot (Marmota sibirica) were the preferred wildlife species. Our spatial analyses showed an unexpected significant positive relation between number of domestic horses killed and distance to the park, as well as a significant negative relation with number of gers (tents) in the area. Compared to randomly selected comparison sites (n  =  36), we found Przewalski foal kills (n  =  36) at sites that were closer to the forest, at higher altitudes, with lower shrub cover, higher forest cover, and higher red deer density. If the negative trend of deer numbers continues and if herdsmen protect their livestock more vigorously, depredation of wild Przewalski horses by wolves will rise. Therefore, a large red deer population could be pivotal in improving the conservation status of Przewalski horses.