Various bat species often occupy the same habitats. Cohabitation should induce different preferences in spatial or trophic components of the bat ecological niche, to reduce their competition. This determines the differences in the trematode fauna of Myotis spp. The purpose of our research was to study the biodiversity of trematodes in syntopic populations of five Myotis species in the Samarskaya Luka National Park. In 2005–2007 we studied 867 bat specimens by the methods of complete helminthological dissection. In total, 11 trematode species were found in Myotis bats. Only three trematode species, Plagiorchis koreanus, Prosthodendrium chilostomum and Parabascus duboisi were revealed in all studied Myotis spp. Prosthodendrium cryptolecithum was recorded for the first time in Russia. Digenean species diversity is higher in Myotis daubentonii and M. dasycneme. The trematode fauna of M. brandtii, M. nattereri and M. mystacinus is less diverse. The determining factor in the infection of bats by trematodes is feeding on semi-aquatic insects, possible second intermediate hosts of these parasites. Our results confirm the data that the ecological niches of the five Myotis species partially overlap. An analysis of the trematode fauna in Myotis spp. showed that in the Samarskaya Luka there may be weak competition for food items among bats.