Rubus hawaiensis is a deciduous shrub known for its distinctive growth form. It typically has erect or arching stems and can reach up to 40 m lengths. These stems are either sparsely branched and covered with slender prickles up to 4 mm long or prickle-free, often exhibiting shredding bark. It is also characterized by its pilose texture, with varying hairiness on different parts. The leaves are compound and palmate, alternating along the stem. They feature three leaflets, with the largest terminal measuring 8–15(–21) cm long and 5–10(–15) cm in width. They are thin, with petiolules (leaflet stalk) that are sparsely to densely covered in hair (or tomentose) and sometimes bear short, slender prickles. The upper surfaces of the leaves are pilose along impressed veins, while the lower surfaces range from moderately to densely tomentose. The leaf margins are coarsely serrate and occasionally lobed, and the petioles and stipules share similar pilose to tomentose characteristics. It produces flowers in small corymbose inflorescences, consisting of 1–4(–8) flowers. They are bisexual, actinomorphic (radially symmetric), and feature a raised receptacle with sepals, petals, and stamens. The sepals are ovate and tomentose, while the petals are dark pink to dusky rose or occasionally white, obovate, and about 13–18 mm long. The numerous stamens have slender filaments and dithecal anthers, and the ovary is superior with a filiform, subterminal style. It bears fleshy fruits that are juicy drupelets, ranging in color from red to dark purple or occasionally yellow, and are roughly 2.5–5 cm long. Each drupelet contains a single seed. It typically inhabits mesic to wet forests and subalpine woodlands between 660-3070 meters.