Cyanea purpurellifolia is a terrestrial shrub that grows 0.2–0.5 meters tall with unbranched, fleshy stems that are unarmed but can be muricate or aculeate. Its leaves are simple and alternate, with narrowly oblong to spatulate blades measuring 12–35 cm in length and 3–6.5 cm in width. The apex is subacute, with glabrous upper surfaces and purple lower surfaces that are glabrous or sparsely pubescent along the veins. The margins are callose–crenulate toward the apex and entire toward the base, with short petioles of 0.5–0.8 cm, and the plant lacks stipules. The inflorescence comprises 3–6 flowers, supported by peduncles of 10–25 mm length and pedicels of 8–15 mm. The hypanthium is cylindrical to obconical, measuring 4–5 mm long. The flowers are bisexual (perfect), with calyx lobes fused into an irregularly 2-lipped or 5-lobed sheath 7–10 mm long. The corolla is zygomorphic (bilaterally symmetric), dark magenta, 6–8 cm long, and can be glabrous or pubescent, with the lobes connate and spreading. The stamens are connate with a magenta, glabrous staminal column and anthers with white tufts of hair, opening longitudinally to release pollen. The ovary is inferior, 2-celled, with axile placentation, and the stigma is 2-lobed. The fruit is a dark purple berry, ellipsoid to obovoid, 15–18 mm long, containing numerous small, shiny, brown to black seeds that are 0.2–0.5(–2) mm long with a straight, short to spatulate dicotyledonous embryo embedded in oily endosperm. It is found at an elevation of approximately 600 meters.