Pittosporum napaliense is a small tree that can reach heights of 5–11 meters, with young parts characterized by pale brown tomentose–strigose covering. The stems of this species are notable for their glabrate branches. The leaves are simple and alternate, with oblong blades, obovate to broadly obovate, measuring (9–)21–31 cm in length and (3–)7–9.5 cm in width. The leaves have an obtuse to rounded apex, sometimes short-acuminate, and an attenuate to cuneate base. The upper surfaces of the leaves feature slightly impressed veins and are glabrate, while the lower surfaces are gray or whitish flocculose–strigose, becoming subglabrate over time. The blades are subcoriaceous, with entire, slightly revolute margins and 8–16 pairs of lateral veins. The petioles are 1.5–5 cm long. The flowers occur in pale brown tomentose–strigose inflorescences, with peduncles 4–30 mm long and pedicels 3–9 mm long. The bracts are subulate to narrowly lanceolate, measuring 9–17 mm long. The plant produces unisexual flowers, numbering 8–20 per axillary or terminal, simple, umbellate inflorescences. The calyx is narrowly cup-shaped and about half as long as the petals, with five distinct, broadly ovate or obovate sepals that are 5–8 mm long, densely pale brown or gray tomentose externally, and minutely pale brown tomentulose within. The corolla comprises 5 cream-colored petals, each 14–18 mm long. There are five stamens alternating with the petals, with filaments approximately 8 mm long in hermaphroditic flowers and 3 mm in pistillate flowers. The fruit is an oblong–ovoid capsule measuring 17–19 mm long, covered in dense whitish, gray, or pale brown tomentum when immature and becoming glabrate at maturity. The persistent style is approximately 4–5 mm long, and the valves have a coriaceous exocarp about 1.5–2 mm thick. The surface of the capsule is shallowly rugose, and the seed mass fills its volume. Seeds are roughly 20 per fruit, black to reddish black, ovoid to irregularly angled and compressed, and 5–8 mm long. It typically grows in disturbed hala forests and mesic valleys between 150–550 meters.