Rhynchospora sclerioides is a perennial sedge with short rhizomes sheathed in brown fibers and stout, trigonous culms (20–)40–90 cm tall that are smooth to scabrous and 1–3-nodose. The leaves are numerous and chiefly basal (with 1–3 lower cauline), linear and flat, as long as or longer than the culm, (5–)7–18 mm wide, long-acuminate at the tip; the lower surface has strongly scabrous margins and midnerve; sheaths are brown. The inflorescence is an elongated, narrow, interrupted, decompound panicle 15–60 cm long bearing 5–9 solitary, pyramidal-ovoid partial panicles (3–7 × 2–4 cm), dense to lax, on 3–7 cm peduncles; bracts exceed the subtended partial panicle. Spikelets are brown to reddish brown, solitary or in pairs/triads, sessile or short-pedicellate, lanceolate and acute, 7–8 mm long; glumes 6–8 in two ranks, the middle 3–4 flower-bearing (typically 2 of them perfect), with the midnerve awned; perianth bristles 5–6, 5–7 mm, antrorsely scabrous and longer than the achene and style base. The flowers are bisexual (occasionally the distal staminate); ovary superior with a pale-brown, subulate-conical style base (~1.5 mm) tapering to a long, 2-cleft style. The fruits are yellowish-brown achenes, obovate to obovate-oblong, dorsiventrally lenticular, 1.2–1.5 mm long (incl. short stipe) and 1–1.3 mm wide, minutely reticulate-cancellate, with a single seed (basal embryo, abundant endosperm). It is found in mesic forest, grasslands, and on ridges between 90-1,220 meters.