Rhizomes erect, apex densely clothed with brown, subulate-lanceolate scales. Fronds caespitose; fertile fronds 34-60 cm; stipe blackish brown, upward stramineous, 17-26 cm, 1.5-2 mm in diam. at base, base similarly scaly, upward glabrate; lamina 2- or 3-pinnate, or 3-pinnate-pinnatifid, ovate, 21-34 × 17-24 cm, base rounded-cuneate, apex acuminate, slightly abruptly narrowed; pinnae 13-16 pairs, basal pinnae subopposite, upper pinnae alternate, slightly ascending, with stalk 1-3 mm; basal pinnae slightly shortened, broadly lanceolate, 7-10 × ca. 2.5 cm, base inequilateral, truncate, auriculate and parallel to rachis on acroscopic side, narrowly truncate on basiscopic side, pinnate, apex long caudate-acuminate, slightly narrowed; pinnules 10-14 pairs, alternate, subspreading, basal pinnules with short stalk ca. 1 mm, upper pinnules sessile, subrhomboid, 1-2 cm × ca. 8 mm (acroscopic pinnules larger than basiscopic pinnules), base inequilateral, subtruncate, somewhat auriculate on acroscopic side, narrowly cuneate on basiscopic side, pinnatilobate to pinnatipartite or biserrate at margin, apex obtuse-rounded or obtuse, toothed; middle pinnae similar to basal pinnae but slightly larger, up to 15 × 2.5 cm, base hardly narrowed; pinnules pinnatipartite, pinnule segments long toothed; sixth to seventh and upper pinnae abruptly narrowed at apex, pinnatipartite, pinna segments subrhomboid, biserrate at margin and apex; veins visible on both surfaces, pinnate in pinnules, lateral veins 5 or 6 pairs, lower veins pinnate, upper veins forked. Lamina thinly herbaceous when dried, green, glabrate on both surfaces; rachis and costae stramineous, glabrate or with short hairs abaxially, with needlelike or subulate spines on adaxial side at base of costa, costule, and midrib. Sori oblong, on basal acroscopic veins, close to costules, 2-4(or 5) pairs per pinnule; indusia brownish, oblong, membranous, erose at margin, persistent, often partly overlapping costules. Perispore surface without folds, with granular ornamentation.

Athyrium nyalamense differs from related species in the lamina ovate, 2-pinnate or 3-pinnate; pinnae 13-16 pairs, lanceolate or linear-lanceolate, 5-15 cm or more; pinnules oblong, separate from each other; pinnule lobes with prominently long or short teeth at margin; and rachis and costae glabrate or shortly hairy abaxially.

Broad-leaved forests; 1400-2400 m. SE Xizang, Yunnan [Bhutan, India, Myanmar, Nepal].