The Soprano pipistrelle is slightly smaller than P. pipistrellus and with a wingspan of 190 - 230 mm. Its dorsal fur is reddish brown, while its snout and ears are short and pale. Another characteristic is its strongly curved forehead.
This is a species strongly dependent on lowlands and riparian forests. Most of its nursery roosts can be found in wall cavities or wall claddings of houses, as well as tree holes. Not much is know about its winter roosts, though it is believed that tree cavities are used.
The agile flight of P. pygmaeus can be observed over water surfaces or around small forest glades. Similarly to P. pipistrellus, its diet comprises of aquatic midges, larvae and mayflies.