Rhizomes short, erect, apex densely clothed with brown, lanceolate scales. Fronds caespitose; fertile fronds 25-70 cm; stipe blackish brown, upward pale green-stramineous, 10-25 cm, 1-2.5 mm in diam., base similarly scaly, upward glabrate; lamina 2-pinnate-pinnatipartite, oblong or oblong-ovate, (10-) 18-45 × (6-)11-14 cm at middle, base rounded, hardly narrowed, apex acuminate; pinnae 10-20 pairs, alternate, ascending, with stalk 3-4 mm; basal pinnae slightly shortened, 2-5 cm; second basal pinnae lanceolate, 6-10 × 2-2.5 cm at base, base equilateral, subtruncate, pinnate-pinnatifid to 2-pinnate, apex long acuminate; pinnules 10-14 pairs, basal pinnules opposite; upper pinnules alternate, ascending, narrowly separate from each other, basal pinnules slightly larger, ovate-oblong, 1-1.3 cm × 4-5 mm at base, base inequilateral, truncate, parallel to costae on acroscopic side, cuneate on basiscopic side, pinnatipartite nearly to costule, apex acute; pinnule segments 4-6 pairs, oblong, acroscopic segments larger than basiscopic segments; basal acroscopic segments largest, with few short teeth; veins visible abaxially, pinnate in lower segments, lateral veins 2 or 3(-5) pairs, upper veins forked. Lamina herbaceous when dried, pale greenish brown, glabrate on both surfaces; rachis and costae stramineous abaxially, with dense short glandular hairs at base of costa, with needlelike spines on adaxial side at base of costa, costule, or midrib. Sori usually oblong, sometimes J-shaped, horseshoe-shaped, or orbicular-reniform, 1 per segment, but 2 or 3 sori in basal acroscopic segments; indusia yellow-brown, polymorphic, membranous, entire, persistent. Perispore surface without folds, with granular ornamentation. 2n = 80, 160.

Athyrium iseanum differs from related species in the lamina oblong or oblong-ovate; pinnules oblong-ovate, pinnatipartite into 4-6 pairs of segments with few short sharp teeth; prominent needlelike spines present on rachis, costae, costules, and midribs; sori oblong, J-shaped, horseshoe-shaped, or orbicular-reniform, indusia entire; and bulbils absent or present in distal part of rachis and also costa.

Valley forests, wet areas; near sea level to 2800 m. Anhui, Chongqing, Fujian, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, Taiwan, Xizang, Yunnan, Zhejiang [Japan, S Korea].