Canavalia molokaiensis is a perennial climber with twining branches, distinguished by its long acuminate leaf apex and rose-purple flowers with distinct white markings. It features compound, alternate leaves with narrowly to broadly lanceolate or sometimes ovate leaflets, measuring 3.5–8(–10) cm long and 1.3–5.4(–6.5) cm in width. The leaf apex ranges from long-acuminate to short-caudate, and the base is cuneate to sub-truncate. The leaf surfaces are sparsely appressed pubescent, becoming more glabrate over time. The flowers are found in axillary pseudoracemes, usually containing 4–15 flowers each, and measure 3–9 cm in length. These papilionaceous flowers have a 20–28 mm long calyx and are sparsely pubescent, with a strongly concave upper edge. The corolla is rose-purple, with the standard petal featuring a white spot and streaks at the base, measuring 39–45 mm long. The fruit is a compressed pod 12–16 cm long and 2.3–3.5 cm wide, with sparsely appressed pubescent surfaces. The seeds are dark reddish brown, oblong-elliptic, strongly compressed, and arranged transversely within the pod with an elongated hilum. Each seed is 20–23 mm long and 14–16 mm wide. It grows in open, dry sites, mesic shrublands, and steep slopes of gulches, predominantly between 850–930 meters.