Erythrina sandwicensis is a tree that can reach heights of 15 meters and is characterized by its reddish, papery, shallowly fissured bark. The trunk and branches are sparsely armed with conical prickles, adding to its distinctive appearance. The leaves are compound, specifically pinnately trifoliolate, and alternate. They are deciduous, typically absent when the tree is flowering. The blades are 4–10 cm long and 6–15 cm wide, with the terminal leaflet being deltate to rhombic-oblate and broader than long, while the lateral leaflets are ovate. The apex of the terminal leaflet is obtuse to rounded, and the lateral leaflets’ apices range from acute to rounded. The base of the terminal leaflet can be truncated or rounded, with lateral leaflets having an asymmetrical base (cuneate on one side and rounded on the other). The upper surfaces of the leaflets are glabrous, while the lower surfaces are densely covered with stellate-tomentose hairs. The leaflet margins are entirely smooth. Each leaf has petioles for the terminal leaflet measuring 8–15 cm and petiolules for the lateral leaflets around 5 mm. Stipules are subulate, about 5 mm long, and are deciduous. The inflorescence is a horizontal axis measuring 10–15 cm long, with flowers present only on the distal half. The flowers are papilionaceous and bisexual (perfect). The pedicels range from 3–10 mm long. The calyx is fusiform in bud, 1.5–2 cm long, with five apical knobs. As the corolla emerges, the calyx splits open on the dorsal side, becoming spathaceous and positioned beneath the corolla. It is thin, chartaceous, and densely covered with brownish, felty, stellate wooly hairs. The corolla is typically orange but can also be yellow, white, or pale green, with the standard (the largest petal) being broadly ovate to elliptic, 4–5 cm long and equally wide, and the wings and keel slightly smaller. The stamens number ten have a monadelphous arrangement where nine are fused most of their length, and one is free. The ovary is superior, with a style that extends 2–2.5 cm and ends in a capitate stigma. The fruit is a pendent pod, slightly constricted between the seeds, and the endocarp is papery. The seeds are red to yellowish-orange, about 15 mm long and 10 mm wide, with a black hilum. They remain persistent on the pods well after the pods have matured. It is found in dry forests at elevations up to 600 meters.