Stenogyne calaminthoides is a scandent or decumbent vine growing several meters long. The stems are sharply or sometimes weakly four-angled, with ridges along the angles, and are typically moderately to densely tomentose, especially along the ridges, though occasionally glabrous individuals may occur. The leaves are simple and arranged oppositely. Blades are narrow to broadly ovate, measuring 2.2 to 5.1 cm long and 1.1 to 3.9 cm wide. Leaf apices are usually obtuse, though sometimes acute, while the bases range from truncate to cordate. Surfaces are glabrous or moderately to densely short-pubescent on the lower surface, and the texture is membranous. The margins are crenate, and petioles range from 4 to 15 mm in length with sparse pubescence. Stipules are absent. The flowers are arranged in axillary verticillasters with typically 6 (up to 10) flowers, each on pedicels 4–9 (sometimes up to 14) mm long. The calyx is zygomorphic (bilaterally symmetrical) with an upper lip of three lobes and a lower lip of two lobes, forming a tubular or narrowly campanulate structure 7 to 14 mm long, which enlarges in fruit. It is glabrous or rarely pubescent at the base, with usually obtuse teeth 1–3 mm long and 2.5–4 mm wide at the base. The calyx splits longitudinally and is usually persistent or partially persistent. The corolla is bilabiate and moderately to densely tomentose on the exterior, particularly on the distal portions. It ranges in color from pink, dark magenta, and purple to, rarely, white with a faint purple tinge. The corolla tube is strongly falcate, narrowly funnelform, and 22–29 mm long. The upper lip is 6–11 mm long and may be entire or 2-lobed, while the lower lip is 3–6 (sometimes up to 7) mm long with three lobes of similar size. The corolla is sparsely to densely pubescent externally and glabrous within, except for occasional glandular pubescence. A nectary disk is often present at the base of the ovary. Four stamens are usually included within the corolla or exserted beyond the upper lip. Both pairs are of similar length, though the upper pair may be slightly longer. Filaments are pubescent and inserted near the throat, and the dithecal anthers have divaricate sacs that open by longitudinal slits. The ovary is superior and 2-carpellate, with each carpel longitudinally divided and basal-axile placentation. Each ovary lobe contains one ovule. The single style is exserted, usually cleft, and diverges after anther dehiscence, ending in two subulate lobes. The stigma has two parts. The fruit is a drupaceous nutlet, 5–6 mm long, black at maturity, and enclosed within the calyx. It is 1-seeded, slightly winged at the margins, obliquely attached at the base, and has a fleshy exocarp. Seeds have scanty to absent endosperm and are oily. It is found in mesic to wet forest and boggy wet forest habitats between 750-1,550 meters.