Cyanea kahiliensis is a shrub that grows between 1 and 4.6 meters tall. The stems are branched and glabrous. The leaves are simple and alternately arranged. The blades measure 8–22 cm long and 1–4 cm wide and are narrowly elliptic or narrowly oblong. The apex is acute or acuminate, rarely obtuse, while the base is cuneate. The upper surfaces are green and glabrous, whereas the lower surfaces are pale green and glabrous. The margins are callose–crenulate. The petioles range from 5 to 16 cm in length and are glabrous. Stipules are absent. The flowers are arranged in axillary inflorescences, each containing 8–10 flowers. The peduncle is 10–80 mm long and glabrous, and the rachis measures 4–14 mm long, also glabrous. The bracts are deltate, deciduous, and measure 0.6–0.8 mm long. The pedicels are 8–18 mm long. The hypanthium is obovoid, 4–5 mm long, 3–4 mm in diameter, and glabrous. The flowers are bisexual (perfect). The calyx has five lobes, which are 0.4–0.6 mm long, deltate or shallowly deltate, distinct or rarely connate, with an acute apex. The calyx tube is adnate to the ovary. The corolla is zygomorphic (bilaterally symmetric), measuring 19–25 mm long, white, sometimes tinged greenish or purplish, and glabrous. The corolla tube is 14–16 mm long and 1.5–2.5 mm in diameter at the middle, suberect or slightly curved, and dorsally cleft for 1/5–1/2 of its length. The lobes are spreading, with dorsal lobes 5–10 mm long and 0.8–1.3 mm wide, linear or linear triangular, with an acuminate apex. The ventral lobes are 5–8 mm long and 1–1.5 mm wide, linear triangular, connate at the base for 2–4 mm, with an acuminate apex. The five stamens alternate with the corolla lobes and are connate, with a slightly exserted staminal column. The anther tube is 1.5–1.9 mm in diameter and glabrous. The dorsal anthers measure 5.2–6 mm long, while the ventral anthers are 4.3–4.8 mm long and bear tufts of hairs at the apex. The anthers are dithecal, opening by longitudinal slits, coherent but separating after anthesis or connate to form a tube into which pollen is shed. The filament tube measures 16–20 mm long and is glabrous. The filaments are distinct or connate above and are attached to the epigynous nectary disk or the base of the corolla, rarely adnate to the corolla tube. The ovary is inferior and two-celled, with axile ovule placentation. The stigma is two-lobed, remaining appressed and nonreceptive as the style grows through the anther tube, pushing out the pollen, after which the stigmas spread apart and become receptive. It is found in diverse mesic and wet forests between 490-800 meters.