The Brandt’s Bat (Myotis brandtii Eversmann, 1845) is one of the rarest bat species in Ukraine. There are only a few known locations of this species in summer and less known hibernacula in the whole country. Moreover, for territory of the north-eastern Ukraine are known only two underground bat hibernation sites with aggregation more than several tens of individuals. We undertook population surveys of winter aggregations in newly discovered and dug up abandoned sandstone mines in the Chuguev district of the Kharkiv Region (49°54′ N, 36°43′ E) from 2007 through 2015. We also surveyed summer bat assemblages in the forests surrounding these mines in 2012. The mines’ microclimate conditions were as follows: temperature +6 °C - +10 °C and humidity 60-80 %. M. brandtii, M. daubentonii (Kuhl, 1817) and Plecotus auritus (Linnaeus, 1758) hibernate in the mines; the first species is most abundant by number of individuals. In midsummer 9 bat species were recorded including the three previously mentioned. M. daubentonii and P. auritus breed in surrounding forest, but M. brandtii does not. One recaptured individual of M. brandtii was minimum 6 years old, providing us the first recorded information on longevity of this species for Ukraine. The total number of bats hibernating in these mines is estimated to be up to 100 individuals; a hibernaculum with several tens of M. brandtii could be classified as more numerous for this species in Ukraine. For this reason, the system of mines in the Kharkiv region needs species protection status and an action plan for monitoring and management.