Euphorbia olowaluana is a tree growing 2–9 meters tall. The stems are 10–20(–30) cm in diameter and can be glabrous to pilose, especially at the nodes. The leaves are simple and opposite, arranged distichously. The blades are elliptic to lanceolate or rarely linear, measuring 20–70 mm in length and 4–15 mm in width. The apex is acute and mucronulate, rarely retuse or truncate. The base is cuneate and oblique. The surfaces are glabrous or pilose on the lower surfaces and at the basal margin. The margins are entire. The petioles are 1–3 mm long with a pilose to glabrate lower surface. Stipules are acute to acuminate–triangular, 1–4 mm long, pilose to villous, erose, and ciliate. The flowers are in cyathia, solitary in the leaf axils, or on shortened, much–reduced branches. The peduncles are 1–3 mm long, glabrous to villous. The involucre is campanulate, 1.5–2(–2.5) mm high and 2–3 mm wide, glabrous or pilose beneath the glands, which number 4 and are pilose to villous. The flowers are unisexual and highly reduced. Pistillate flowers are solitary on a gynophore, while staminate flowers are in 5 groups or cymules, each with 1 to several flowers. The calyx (sepals) and corolla (petals) are absent. Male flowers are reduced to a single stamen with an articulation at the junction of the pedicel and filament, subtended by slender bracteoles. The ovary is superior with red styles that are bifid at least half their length, 0.5–1 mm long, and pubescent, with a thickened stigma. The capsules are green, 2–3.5 mm long, glabrous to pilose, with recurved gynophores exserted 2–4 mm from the involucre and pilose. The seeds are gray to brown, 1.5–2 mm long, and rugose. It is found in dry and open subalpine forests between 600–2,800 meters.