Astragalus alopecurus can reach a height of. The hairy stem has a diameter of about 10 mm. Leaves are petiolated, long, with rachis covered with ascending hairs. Leaflets are ovate to elliptic, in 20-25 pairs. The inflorescences are in clusters subsessile or with peduncle up to 1 cm, ovoid to cylindrical,, while bracts reach. Petals are yellow and glabrous. This plant blooms from June to August.