Pittosporum hawaiiense is a small tree in the Pittosporaceae (pittosporum) family. Trees are 3.7 to 4.6 m (12 to 15 ft) tall with straight ascending branches and white bark. Leaves are scattered or are arranged in distinct whorls; large, ovate-oblong shaped, 13 to 25 cm (5 to 10 in) long, and 3 to 8 cm (1 to 3 in) wide. However, the largest specimen of this species, which is also the largest in the genus, was collected in the Kohala mountains with leaves measuring 35.5 by 10 cm (14 by 4 in). Leaf blades are brown or reddish brown, hairy to smooth, drying green to brown. Flowers are clustered on terminal and axillary (between branch and stem) or cauline (growing on the stem) stalks 10 to 20 cm (4 to 8 in) long. Most Hawaiian Pittosporum species have functionally unisexual flowers and are monoecious, including P. hawaiiense. Ovaries and stamens are in separate flowers, located within the same cluster. Sterile inflorescences mostly occupy the apex or upper leaf-whorls, and the fertile ones the lower whorls or the bare branch. The corollas are cream colored with a 7.6 cm (3 in) tube. The seed capsules are 3 cm (1.2 in) or more in diameter, and are deeply wrinkled. Deeply black or reddish, resin-covered seeds are embedded in orange aromatic pulp that is displayed when the seed capsules open. Each capsule contains approximately 30 seeds.