ðə lˈɔŋtˈeɪld bˈæt ɪz ɐ smˈɔːl bɹˈaʊn bˈæt wˈeɪɪŋ ˈeɪt twˈɛlv dʒˈiː wɪð ɐ lˈɔŋ tˈeɪl kənˈɛktᵻd baɪ ɐ pˈæɾɪdʒəm tʊ ɪts hˈaɪnd lˈɛɡz: ðɪs fˈiːtʃɚ dɪstˈɪŋɡwɪʃᵻz ɪt fɹʌm nˈuː zˈiːləndz ˈʌðɚ bˈæt spˈiːsiːz, ðə ʃˈɔːɹttˈeɪld bˈæt mˈɪstɐsˌɪnə tˌuːbɚkjʊlˈɑːɾə.
The long-tailed bat is a small brown bat (weighing 8–12 g) with a long tail connected by a patygium to its hind legs: this feature distinguishes it from New Zealand's other bat species, the short-tailed bat (Mystacina tuberculata).