Eurycea nana averages about 2 inches long, but may reach up to 3.25 inches. It is the smallest of the Euryceas and is slender with short limbs, the back limbs having 5 toes and the front limbs 4. Gill fringes are prominent behind the head and there are also 16-17 costal grooves. It is light brown on its back, yellowish white ventrally, with pale yellow flecks obvious on the midline. Distinctive large eyes have a dark ring around the lens.
Males have more poorly defined mental and caudal hedonic glands than females.
Developed, pigmented gills are maintained throughout adulthood, but gases are exchanged almost entirely through cutaneous respiration. The vents of males are lined with papillae, contrasting with the smooth folds in females. This species is voiceless and earless. Reproduction Males are sexually mature at 19 to 23.5 mm and females when they are longer than 21 mm. Strongly acyclic oviposition and the presence of gravid females and very small larvae during every month of the year suggests that breeding is occuring year round.