Bryum leptocladon is one of the smallest Bryum species in Central America. It has erect‑imbricate, short, broad leaves that are not or scarcely bordered, a stout costa that is percurrent to shortly excurrent and thin‑walled leaf cells that are rhomboidal above but rectangular below. Its capsules are short, suberect and have sharply constricted necks. Bryum leptocladon is a nondescript moss that appears to be common in the Caribbean but is otherwise rare and locally distributed. Ochi (1980) attributed its anomalous distribution to the simple failure to recognize it outside the Caribbean.

In size and gross aspect it is similar to Bryum argenteum, B. chryseum, and B. dichotomum. All three the above species differ from B. leptocladon in having leaves with thicker‑walled cells and quadrate basal cells. Other features distinguishing B. leptocladon from these three species include the silver color of B. argenteum, the long-excurrent costae of  B. chryseum and B. dichotomum, and the quadrate stem epidermal cells of B. chryseum. Although the leaf areolation of B. coronatum is similar to that of B. leptocladon, B. coronatum is a larger plant (to 2 cm high) with longer leaves (1–3 mm long), and short, broad‑necked capsules. The leaves of B. apiculatum and B. subapiculatum are similar to those of B. leptocladon in more or less lacking a leaf limbidium, but the leaves of both species are more than 1 mm long and have quadrate basal cells.