Schenkia sebaeoides is an erect, glabrous annual herb, standing 6–20 cm tall. Its stems are solitary or branched below and almost always within the inflorescence. It has simple, opposite leaves. The leaf blades are obovate or broadly elliptic, measuring 0.7–3.2 cm in length and 0.4–1.4(–2.3) cm in width. They have an obtuse apex and a somewhat clasping base, are slightly fleshy, and display entire margins. The leaves are 3(5)-veined, sessile, and sometimes clasping the stem. Stipules are absent. The flowers are arranged in elongate, spike-like cymes, each being bisexual (perfect) and actinomorphic (radially symmetric). The calyx is (4)5-lobed, deeply cleft, with linear lobes that are 7–8 mm long and have often scarious margins. The corolla is white to very pale pink, (4)5-lobed, with a tube measuring 7.5–10 mm long and lobes that are 4–4.5 mm long, narrow, and usually emarginate at the apex. There is a nectary disk or distinct nectary glands usually surrounding the ovary. The stamens are typically exserted and alternate with the corolla lobes; anthers are dithecal, opening by longitudinal slits or rarely by terminal pores, and become spirally twisted after dehiscence. The ovary is superior, 2-carpellate, 1-celled, with parietal placentation, sometimes deeply intruded; it usually contains numerous anatropous ovules. The style is terminal, filiform, simple or 2-lobed, deciduous, wet, and papillate. The fruits are septicidal capsules, cylindrical in shape, 8–9.5 mm long, with two valves. The seeds are numerous, brown, approximately 0.45 mm long, with a reticulate surface and oily endosperm. It is found in scattered and rare occurrences on volcanic or clay soil in dry, rocky coastal sites between sea level and 150 meters.