Nyctalus leisleri mostly roosts in tree cavities in summer, but bat boxes or buildings may also be used. It hibernates in tree holes, but also buildings or underground sites. This bat forages on the wing and its echolocation and wing morphology are best suited to track and capture small to medium prey in open space, often comprising Nematocera, Trichoptera, Coleoptera, and Lepidoptera, but also prey associated with farmland (Hemerobiidae, Chrysopidae, and Ichneumonidae) or, in England, Ireland, and Germany, with pastoral activity such as Scathophaga stercoraria, Scarabaeoidea and associated Acari (reviewed in Stone et al. 2020). The species may fly at altitudes > 10,000 m asl (Jenssen et al. 2019).

A long-distance migratory species in most of Europe, N. leisleri moves seasonally between summer roosts in northeast Europe and hibernacula in southwestern Europe (Hutterer et al. 2005). The longest seasonal movement (1,567 km) was recorded between Dresden, in Germany, and Burgo, in Spain (Hutterer et al. 2005). There is evidence that some populations do not migrate but reproduce and hibernate where winters are mild (Hutterer et al. 2005, Boston et al. 2020).

In Europe, Nyctalus leisleri is distributed from Ireland eastwards through central Europe as far as the Urals. Northwards, it reaches southern Scotland and latitude 57°N on the mainland, and in the south, it occurs in continental Italy, Corsica, Sardinia, Madeira, the Canary Islands, Greece, Crete, and Cyprus (reviewed in Boston et al. 2020). The range of altitudes where this species can be found varies between 0 and 2,400 m asl. AOO and EOO have not been estimated, but based on the available locality records, they are expected to greatly exceed the threshold for a threatened category. Out of Europe, it is found in northwest Africa (Morocco, Algeria, and Cyrenaica), Afghanistan, Western Himalayas, and Central China (Boston et al. 2020).

Nyctalus leisleri is protected by national legislation in most range states. There are also international legal obligations for its protection through the EUROBATS Agreement and Bern Convention, where these apply. It is included in Annex IV of the EU Habitats & Species Directive. According to the 2013-2018 art. 17 reporting done under 92/43/EEC Habitats Directive (https://nature-art17.eionet.europa.eu/), the species has an unfavourable-inadequate conservation status in all biogeographic regions except the Boreal region, where its conservation status is listed as unknown. Protection of suitable tree roosts and unmanaged forest patches is essential for the conservation of this species. In regions where bats roost in buildings, such sites also need strict protection. Leisler's Bats are also victims of wind turbines, so careful impact assessments and the application of appropriate mitigation measures are needed where relevant.