Zanthoxylum dipetalum var. tomentosum is a tree that can reach heights of 4–15 meters. The trunk, which can be up to 30 cm in diameter, features finely fissured-reticulate bark. The new growth on this tree is glabrous or finely puberulent to tomentose, and a pair of bud scales subtend young branches. It has compound, alternate leaves with 3–7 thick and coriaceous leaflets. The lowest pair of leaflets is strongly reduced, measuring only (0.2–)1.5–3(–4) cm long, and sometimes one or both of these leaflets are absent. The leaflets range from 6–15(–36) cm in length and (2.5–)3.5–9(–13.5) cm in width, with lateral petiolules articulated only at the base, 3–9 mm long, and a terminal petiolule that is twice articulated, at the base and near the leaflet, 8–30 mm long. These leaflets are oblong-elliptic, elliptic to broadly elliptic, or sometimes broadly obovate, with obtuse to rounded apices and a cuneate to rounded base. The lower surfaces are puberulent, especially along the midrib, and are conspicuously glandular punctate. Margins are entire and rarely weakly emarginate. The rachis is terete (cylindrical) or winged, and stipules are absent. The flowers occur in terminal or leaf-opposed, open, cymose inflorescences usually 5–10 cm long, with peduncles 10–40 mm long and pedicels 3–6(–8) mm long, subtended by a pair of bud scales. These flowers are unisexual and actinomorphic (radially symmetric), with a calyx of 4 sepals that are broadly ovate-deltate and 1–1.5 mm long, ciliolate. The corolla comprises two or sometimes four petals: white or yellowish-white, sometimes tinged reddish, lanceolate to ovate, and 6–10 mm long. Stamens are 4, alternate with the petals, glabrous or pubescent, and absent in pistillate flowers. The anthers are medifixed and dithecal. The ovary is superior, 2-carpellate, but usually only one carpel develops, with a rudimentary version in staminate flowers. The style is short and ± coherent, with obliquely orbicular capitate stigmas. The fruits are 1–2 follicles, ovoid, 15–25(–33) mm long, glandular-pitted, with a conspicuously beaked apex 3–8 mm long. The exocarp is rugose, and the endocarp is coriaceous. Usually, one seed per follicle, black, ovoid, 13–14 mm long, is attached by a slender funicle. It is found in dry to mesic forests and sometimes along the margins of wet forests between 260-1,280 meters.