N. jamaicensis has a head and body length of 35-55 mm, tail length is 50-60 mm, and forearm lengths of about 27-41 mm. And adult weights are about 4-10 grams. The long, soft fur is generally gray, buff, yellowish, reddish, or deep chestnut.

N. jamaicensis is slim-bodied with long and slender wings, legs, and tail. The large, separate ears are funnel shaped and are studded with glandular papillae, similar to those found in the Old World vespertilionid genus Kerivoula. Adult males also have a large structure on the face or muzzle, called the "natalid organ" which is composed of cells that show resemblance to sensory cells, but may also have a glandular function. The muzzle is elongate and lacks a nose-leaf. The broad lower lip is reflected outward in the front and often has transverse grooves.

In general, N. jamaicensis roosts with other bats in the darkest recesses of caves and tunnels and can be distinguished from other species by its fluttering, mothlike flight. They are insectivorous. They are sometimes found in large groups, but also congregate in groups of fewer than a dozen individuals.

N. jamaicensis is found in Jamaica.