Body length: 4-5.5 cm

Body weight: 6–13 g

Wingspan: 26–29 cm

Colour: barbastella is one of the most easily recognisable Polish bats due to the characteristic, triangular shape of the ears touching above the short nose, a small, delicate mouth and a very dark, almost black skin and fur. The hair is thick, long, silky and gives the impression that it is dusted, as the hair on the back has white or yellowish endings. It has a grayish belly.

Life expectancy: on the basis of girdling, it is known that the age of some organisms in the wild may even exceed 20 years, but on average they live from several to a dozen or so years.