To determine the species composition of bat flies (Diptera: Nycteribiidae) in Belarus and to indicate their areas of distribution and hosts. To establish the taxonomic position of Belarusian specimens of Nycteribiidae.Own collection of bat flies, collected in 2019–2023 in Belarus. Species identification was carried out both by morphological characteristics and using molecular genetic methods.There species preferences on hosts of bat flies in Belarus: P. monoceros is found mainly on M. dasycneme, recorded in the northern part of the country; N. kolenatii is widespread throughout Belarus, and recorded only on the M. daubentonii. Deviations of some morphological characteristics from the keys and descriptions of the species of the N. kolenatii individuals studied were revealed. The individuals presented in GenBank as N. kolenatii represent three different genetic lines. The Belarusian samples belong to the central haplotype KH1.Bat flies in Belarus were found on two species of bats: M. daubentonii and M. dasycneme. The genetic heterogeneity of representatives of N. kolenatii and the detected variability of taxonomically significant morphological characters may indicate both incorrect species identification of N. kolenatii sequences deposited in GenBank, as well as the presence of cryptic species among representatives of this group. The hidden genetic diversity and identified morphological features of species of the genus Nycteribia require further study, including taxonomic revision based on comprehensive morphological and genetic analysis.