Peperomia leptostachya is a fleshy herb characterized by its green or reddish-green stems ascending or erect from a repent base. It typically reaches 15–25 cm heights and diameters up to 6 mm at the base. The leaves are simple, opposite, or sometimes whorled (3 per node). Leaf blades range from elliptic-obovate to elliptic, measuring 1.5–6 cm in length and 1.2–2.5 cm in width. They have broadly acute to rounded apices and cuneate bases, sometimes broadly so. The leaf surfaces are finely hirtellous and green, with the lower surfaces being paler and deciduous. The leaves are moderately firm-fleshy, thin, and membranous when dry. The petioles are 0.5–1 cm long and finely hirtellous. It produces numerous flowers in axillary and terminal spikes, ranging from 4.5 to 13 cm in length, with some as short as 3 cm. The rachis is about 0.5–1 mm in diameter and glabrous. Flowers are moderately to loosely congested on peduncles that are 0.5–2.5 cm long and finely spreading to appressed hirtellous. Each flower, which lacks a perianth, is subtended by a peltate bract. The fruits are broadly obovoid, measuring approximately 0.9–1 mm long, and are papillose-viscid with sessile glands. Each fruit contains a single seed with scanty endosperm and a copious amount of starchy perisperm. It is found on rocks, ledges, cliffs, and ‘a’a lava and is rarely found as an epiphyte in dry to mesic forests and occasionally in wet forests between 10-610 meters and occasionally up to 1,675 meters.