Herbs perennial, (0.5-)1-2 m tall, tomentose above. Root to 15 cm in diam. Trichomes flattened, crisped. Caudex considerably thickened. Stems erect, branched above. Basal and lower cauline leaves oblong or oblanceolate in outline, pinnatisect, 15-60 cm, glabrous or sparsely pubescent; lateral lobes 6-12 on each side, oblong or lanceolate, 6-20 × 1-5 cm, base decurrent, margin serrulate, sinuate-dentate, or subentire, apex acuminate. Upper cauline leaves auriculate, similar to lower ones but gradually reduced in size. Fruiting pedicels slender, 1.5-4 cm, strongly recurved, pubescent. Sepals yellowish, oblong, 3.5-5(-6) × 1.5-2.5 mm, sparsely pubescent or glabrous. Petals pale yellow, oblong or obovate, entire, 4-6(-7) × 2-4(-6) mm, base cuneate, apex rounded to subacute; claw 1-2 mm. Stamens (8-)12-16(-24); filaments 3.5-5 mm; anthers narrowly oblong, 1-1.3 mm. Fruit halves suborbicular to obovate-orbicular, 3-4 × 2.5-3 cm; wings 5-10(-18) mm wide; replum 7-16 mm; locule 1.5-2(-2.8) × 1.2-1.7 cm. Seeds brown, broadly ovate, 1.4-1.7 × 0.7-1.1 cm. Fl. May-Aug, fr. Aug-Oct.

Megacarpaea bifida Bentham, a little-collected and poorly known species endemic to Kashmir, is probably conspecific with (or at most infraspecific under) M. polyandra. It has entire leaf lobes and slightly elongated fruit halves. Megacarpaea polyandra is the only species in the Brassicaceae with flowers having more than six stamens.

The young leaves are cooked as a vegetable.

Slopes, rocky areas, along streams; 3000-4600 m. Xizang [India, Kashmir, Nepal, Pakistan].