Argyrolobium robustum is an erect, sparsely branched, perennial herb, woody at the base, with annual stems that are triangular in cross-section. It grows up to 0.75 m tall. The leaves are smooth, greenish-grey, slightly fleshy but often covered with silky hairs on the lower surface when young. Leaf stalks are 15–40 mm long and grooved, the leaflets are 20–80 mm wide and 50–170 mm long, narrowly to broadly obovate, with rounded apices. Flowers are produced in spring and early summer (Sep. to Jan.), in racemose inflorescences (a central flowering stem with individual flowers each borne on a shorter stalk), up to 400 mm long, with 20–62 flowers. The flowers are yellow with red veins. The calyx is 2-lipped and covered with fine silky hairs. The standard (upper) petal is suborbicular, while wing petals are more or less obovate and slightly longer than the inner, beaked keel. Pods are ± 60–85 mm long and 4 mm wide, linear, compressed, sparsely sericeous and pointing upwards. Seeds are 2–3 mm long, irregular in shape or suborbicular, compressed, light brown and sometimes recalcitrant (wet).