Cyanea lanceolata is an unbranched shrub growing 1–3 m tall. The stems are woody and muricate in juveniles but become scabrous or nearly smooth with age. Its leaves are simple and alternate, with elliptic or oblanceolate blades measuring 15–60 cm long and 5.5–14 cm wide. The leaves have an acute to acuminate apex and are glabrous on the upper surface, though they can be muricate in juvenile plants. The lower surfaces are pubescent with simple hairs or occasionally glabrous. Margins are callose-crenulate, becoming coarsely callose-dentate in younger plants, with petioles ranging from 1 to 9 cm long, either pubescent or muricate.  The axillary inflorescences comprise 4–16 flowers, with peduncles 20–100 mm long and pedicels 5–30 mm long. The hypanthium is obovoid, obconical, or ellipsoid and glabrous. The bisexual (perfect) flowers have triangular calyx lobes, 1–3 mm long and glabrous, with an apex ranging from acute to obtuse. The corolla, pale to dark magenta or occasionally pale greenish with possible longitudinal stripes, is 5–8 cm long and glabrous, with a tube that is suberect to strongly arcuate, cleft dorsally about halfway up, and lobes that are connate and spread. The stamens are connate, with a glabrous or pubescent staminal column and pubescent anthers that have apical tufts of white hairs and open by longitudinal slits; these are coherent but separate after anthesis or remain connate, forming a pollen-containing tube. Its fruit is an obovoid to obpyriform berry, 16–20 mm long, containing numerous small, brown to black seeds, ca. 0.6–0.7 mm long, smooth, shiny, with a straight, short, to spatulate dicotyledonous embryo embedded in an oily endosperm. It occurs in mesic valleys and wet forests, with an elevation range of 300–915 meters.