Pittosporum argentifolium is a small tree growing 6–9 meters tall, with young parts densely covered in pale brown to whitish strigose–tomentose hairs. The stems have branches that are whitish to pale brown and flocculose–strigose. The leaves are simple, alternate, and oblong–elliptic, oblong–oblanceolate, or oblanceolate, measuring (9–)15–30 cm long and 3.4–8(–9) cm wide. The apex is acuminate to acute, while the base is attenuate. The upper surfaces have slightly impressed veins, are whitish flocculose strigose, and become glabrate with age. The lower surfaces have slightly raised veins and are densely whitish to pale brown flocculose–strigose, with hairs sometimes forming a skin-like layer. The blades are subcoriaceous to coriaceous. The margins are entire and slightly revolute. The lateral veins are in 13–25 pairs. The petioles are 1.5–3 cm long. Stipules are absent. The flowers are arranged in inflorescences that are densely pale brown to whitish strigose–tomentose. The peduncles are 4–30 mm long, with pedicels measuring 2–6 mm long. The bracts are subulate and 7–8 mm long. The flowers are unisexual, occurring in groups of 10–20 in axillary or cauline, simple, corymbose inflorescences. The calyx is broadly cup-shaped with five distinct, ovate sepals 3–3.5 mm long, densely pale brown to brown tomentose, with acute apices. The corolla consists of five white petals, approximately 13 mm long. The fruit is a capsule that is ovoid to obovoid or subcuboid, measuring 18–30 mm long. It is densely pale brown to whitish tomentose when immature and usually sparsely so at maturity. The apex is rounded to truncate or occasionally subcordate, with a persistent style approximately 2–3 mm long. The valves have a 2–3 mm thick woody exocarp featuring a median furrow and a shallow to deeply rugose–tuberculate surface, with narrow troughs between the convolutions. The seed mass fills the capsule’s volume. There are about 15–18 seeds, which are black, irregularly angled, and compressed, measuring approximately 6–7 mm long. It is found in dry to mesic forests between 330-1,530 meters.