Cyanea truncata is a shrub that grows 0.3–2 meters tall, with stems that are unbranched or sparingly branched from the base and muricate. The leaves are simple and alternate, with obovate blades measuring 22–60 cm in length and 10–26 cm in width, having an acute to acuminate apex and a cuneate to truncate base. The upper surfaces are green and glabrous, while the lower surfaces are pale green, pubescent, and sparsely muricate. The margins are callose-denticulate, and the petioles, 8–25 cm long, are muricate. It has 8–40 flowered inflorescences that are horizontal to pendent and pubescent, with a peduncle plus rachis length of 40–280 mm and pedicels 10–28 mm long. The hypanthium is obconical, measuring 5–6 mm in length. The calyx is 5-lobed, with narrowly oblong lobes 4–10 mm long and 2–4 mm wide, pubescent, and has an obtuse apex. The corolla is white, striped, or suffused with magenta, 32–42 mm long, and 5–9 mm wide, pubescent, with a curved tube dorsally cleft to about the middle. The stamens are five in number, alternate with the corolla lobes, and connate, with a glabrous staminal column and anthers that are glabrous and have apical tufts of white hairs on the lower two. The ovary is inferior and 2-celled, with axile ovule placentation. The fruit is an orange, globose berry, 8–10 mm long, containing numerous small, brown to black seeds, 0.8-1.0 mm long, that are smooth and shiny and have a straight, short to spatulate dicotyledonous embryo embedded in oily endosperm. It occurs in mesic forests at elevations of 240–400 meters.