A typical forest bat that, in summer, typically forms small reproductive groups of adult females (a dozen or so) and their pups in tree cavities (especially under flaking bark in dead trees) or more rarely rock crevices. Infrequently, larger reproductive colonies may be observed in buildings or bat boxes. Barbastelle bats often switch between different roosts, which implies that large numbers of suitable trees need to be preserved to ensure the viability of even small populations (reviewed by Russo et al. 2020). Hibernation colonies may be numerous (up to > 1,000 bats) and are found in caves or bunkers. The barbastelle bat forages in a range of habitats besides forests, including riparian vegetation and farmland, and shows a diet mostly comprising moths, which are caught on the wing. Tympanate prey is caught thanks to a "stealth echolocation" strategy (Russo et al. 2020). A sedentary species that mostly undertakes short moves, the longest-documented one being 290 km in Austria (Hutterer et al. 2005).

The Western Barbastelle (Barbastella barbastellus) has a broad (yet highly discontinuous) European range, from Portugal and the Canaries east to Italy, the Balkans, Belarus, to Ukraine (mainland and Crimea) and European parts of Türkiye, north to 60°N in the Scandinavian Peninsula – south-eastern Norway (where it had been considered to be extinct, but there have been recent sightings), Sweden, and Great Britain (reviewed in Russo et al. 2020). It also occurs on several major islands, including Sardinia, Sicily, Corsica, the Balearic Islands, and – with an endemic subspecies, B. barbastellus guanchae – on the Canary Islands. Despite their small size, both Capri (Italy) and the Isle of Wight (UK) are known to host this species, which is less commonly found on small islands. A record for this species was previously included in error for Ireland; more recent surveys have established that this species does not occur in that country (F. Marnell pers. comm.). The range of altitudes where this species can be found varies between 0 and 2,260 m asl.

Out of Europe, the range extends through the Russian Northern Caucuses to the Caucuses to Georgia, Anatolia (Türkiye), and it occurs in the mountains of Morocco (Rif, Middle Atlas, High Atlas).

The species 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. It is included in Annexes II and IV of the 92/43/EEC "Habitats" Directive, which requests the designation of Special Areas for Conservation. Article 17 reporting produced under such Directive for the period 2013-2018 has established that both habitat and population prospects are either poor or unknown in all biogeographic regions. 2,207 Natura 2000 sites include this species in their designations (EEA 2023).

Preserving Barbastelle populations requires maintaining landscape heterogeneity and protecting unmanaged forests, which may include standing dead trees used as roosts by this species. To support the Barbastelle's main prey, moths, the use of pesticides should be avoided. Additionally, it is important to protect underground sites used by this species for hibernation from human disturbance.