Geranium kauaiense is a decumbent (reclining) subshrub in the Geraniaceae (geranium) family. Stems are reddish brown, often rooting at the nodes, growing embedded in moss mats or other bog plants, 49 to 100 cm (1.6 to 3.3 ft) long, with branches covered by persistent stipules (leaf-like appendages) and leafy only at the ends. Leaves are alternate, oblong to oblong cuneate (longer than broad, parallel sided, sometimes tapering to a point at the base), 1.1 to 2.9 cm (0.4 to 1.1 in) long, 0.4 to 0.8 cm (0.2 to 0.3 in) wide, with the upper surface glabrous (hairless), the lower surface densely silky strigose (with stiff, flattened hairs), and margins entire (edges continuous) except four- to five-toothed at the apex. Flowers are usually three to four in terminal cymes that project beyond the leaves. Petals are white with purple veins, narrowly obovate (egg-shaped and attached at the narrow end), and 9 to 16 mm (0.4 to 0.6 in) long. Immature carpel bodies are 2 to 7 mm (0.08 to 0.3 in) long and densely pubescent (hairy).