Euphorbia celastroides var. kaenana is a shrub or small tree that grows between 0.4 and 9 meters tall. The stems are prostrate to erect, glabrous, and often nodose, measuring 1–6 mm in diameter. The leaves are simple, opposite, and distichous, with blades that are oblong, obovate, or oblanceolate to elliptic or linear, ranging from 4 to 80 mm long and 3 to 40 mm wide. The apex can be acute, obtuse, retuse, or mucronulate, while the base is cuneate to obtuse and oblique. The surfaces are glabrous and sometimes glaucous, with entire margins. Petioles measure 0.5–6 mm long and are glabrous to villous. Stipules are acute to rounded–triangular, 1–6 mm long, glabrous to villous, erose, and ciliate. The flowers are in cyathia on compact lateral branches, with the involucre being campanulate, 1.5–3 mm high, 2–4 mm wide, and glabrous to villous. The glands are 4–5, green or red, and glabrous to pilose. The pistillate flowers are solitary on a gynophore, and the staminate flowers are in 5 groups or cymules, each with 1 to several flowers. 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 yellow, green, or red styles, bifid less than ½ to more than ½ their length, measuring 0.5–1.5 mm long, and glabrous to pubescent, with a thickened stigma. The fruit is a capsule that is green to brown, ovoid to rounded–triangular, 0.5–4 mm long, and glabrous to pubescent, with gynophores that are erect and exserted 0.5–1 mm from the involucre, glabrous to pubescent. The seeds are brown to gray, approximately 1.5 mm long, tetragonal to obcompressed, and smooth to rugose. It is found in coastal dry open areas and mesic forests at elevations ranging from 1-120 meters.