Stems erect. Leaves monomorphic, erect, 1--1.5 dm; bulblets absent. Petiole 1/6--1/4 length of leaf; scales tan, sparse or falling off early. Blade linear-lanceolate, 1-pinnate, gradually tapered to base. Pinnae ± deltate to ovate, slightly overlapping, in 1 plane, 4--8 mm; base truncate, acroscopic auricle well developed; margins denticulate, not spiny; apex rounded, not dentate; microscales linear, lacking projections, dense on both surfaces. Indusia entire to minutely erose-dentate. Spores brown.

Growing in crevices of rocks; of conservation concern; 0--400 m; Alaska.

Polystichum aleuticum is known only from Atka and Adak islands, Alaska. Its nearest relatives are in southwest China. Polystichum aleuticum resembles the dwarfed plants of P . kruckebergii , but it differs, especially, in its smaller, more rounded pinna apices and more abundant scales.