[6][1][7] The species was recognised by Oldfield Thomas in his examinations of the genus, and indicated the diversity by three subspecies, The lesser long-eared bat is a medium-sized species, weighing 6 to 12 grams,[9] with a forearm length ranging from 30.6 to 41.7 mm; it also has long ears which can vary between 17.6 and 25.3 mm in length.

[9] The distinguishing feature of this species is a nose ridge around 1.5 mm high,[10] split and connected by an elastic membrane of skin, creating a Y-shaped groove behind the nostrils.

[11][9] When flying this species will point the tips of its ears forward listening for sound emitted from small openings located at the top of their snouts.

In open areas they will spiral around bushes and shrubs, if they spot prey on the ground they can land capture their victim and then relaunch almost vertically.

[1] The most widely distributed of the genus Nyctophilus, ranging arid to wet regions, they are nevertheless absent from the northeast tropical coasts and Cape York Peninsula.

[9] They occur near the city of Perth at Kings Park, Western Australia with other microbat species, the wattled Chalinolobus, C. morio and C. gouldii, and tiny endemic freetail Mormopterus kitcheneri.

Their preferred roosting places tend to be small crevices such as peeling and hanging bark, in tree hollows, caves, buildings and fairy martin (Petrochelidon ariel) nests, rolled up swags, under piles of bricks and hanging clothes, or occupying the exhaust of a tractor in one instance.

[11] A study from the Journal of Comparative Physiology found that "the first evidence that Australian long-eared bats exhibit similar thermal characteristics and patterns of torpor to their relatives from the northern hemisphere" and "… was used frequently and reduced energy expenditure substantially it appears that it plays a central role in the biology of Australian microbats.

In late August to September ovulation and fertilisation takes place, with gestation lasting between 72 and 93 days.

In late October through to November (later in lower latitudes and elevations) births take place, the mother often producing twins.