Pittosporum confertiflorum is a shrub or small tree ranging from 2 to 9 meters tall. The young plants are characterized by dense reddish-brown to brown or occasionally part pale brown and part whitish tomentose growth. The branches exhibit a reddish-brown to dark brown tomentose coloration that becomes subglabrate over time. The leaves are simple and alternate, with broadly to narrowly obovate or spatulate blades that measure 7–30 cm in length and 1–11 cm in width. The apex of the leaves ranges from obtuse to rounded or acute to occasionally short-acuminate, and the base is attenuate. The upper surfaces of the leaves feature prominently impressed veins, which are initially tomentose but become glabrate shortly after. The lower surfaces are densely or moderately tomentose, especially evident in plants from O’ahu, and the leaves are subcoriaceous to coriaceous and moderately rugose. The margins of the leaves are entire and slightly to strongly revolute. It produces densely tomentose flowers and is located on 3–25 (–55) mm long peduncles. The flowers, which can be either bisexual (perfect) or unisexual, are arranged in terminal, axillary, or cauline simple corymbose inflorescences, typically numbering 5–14 per group. The calyx is broadly cup-shaped, with five distinct sepals lanceolate to broadly ovate or suborbicular, measuring 2–7 mm long and densely covered in tomentose. The corolla consists of white to cream petals that are 13–23 mm long. The stamens are distinct, and the ovary is superior, 2-carpellate, and 2–3-celled, with numerous ovules arranged in two rows per placenta. The fruit is a capsule that is ovoid to broadly ovoid, densely brown to reddish-brown, sometimes compressed, and measures 20–35 mm long. It is initially densely tomentose and becomes sparsely so at maturity. The seeds are approximately 30–50 in number, black to brown or reddish-black, irregularly angled and compressed, or subreniform, and measure 6–8 mm in length. It inhabits various environments, from dry to wet and subalpine forests between 180-2,200 meters.