Portulaca sclerocarpa is a perennial herb with stems that are prostrate to weakly ascending, reaching up to about 20 cm long. The roots are fleshy and tuberous, becoming woody over time. The leaves are simple and can be alternate or opposite, with subterete blades that are 8–12 mm long and about 1.5–2.5 mm wide. The surfaces are pale grayish green, linear, and sessile, with the upper leaves occasionally involucrate around the flowers. The leaves are succulent, with a dense tuft of yellowish-brown hairs about 3–6 mm long in the axil. The margins are entire, and the leaves are sessile. There are two stipules, which are connate basally. The flowers are arranged in dense, terminal, head-like cymes, with 3–6 flowers subtended by dense tufts of hairs 5–8 mm long and a series of involucrate leaves. The bracteoles are about 1.5 mm long. The flowers are bisexual (perfect), actinomorphic (radially symmetric), rarely slightly irregular, and sessile or subsessile. The calyx consists of 2 sepals, which are imbricate, persistent, and about 5 mm long, with scarious margins. The corolla has 4–6(–8) white, pink, or pink petals with a white obovate, base, about 10 mm long, distinct or connate at the base, and imbricate. There are about 30 stamens, with usually puberulent filaments and dithecal anthers that open by longitudinal slits. The ovary is partly inferior, 2–3(–9)-carpellate, soon becoming 1-celled, with numerous ovules and free-central placentation. The styles number 2–9 and are 8-branched. The fruit is a membranous, broadly ovoid capsule, 4–4.5 mm long, indurate, with 0.18–0.5 mm thick walls, and indehiscent or tardily circumscissile about one-third from the base. The seeds are dark reddish-brown, glossy, about 0.4–0.6 mm long, with a stellulate-rugulose surface. It is found in dry habitats such as subalpine woodlands, bare cinders, and near steam vents between 1,030-1,630 meters.