Phyllostegia racemosa is a scandent vine with a spicy odor in its foliage. The new growth is sub-tomentose, and the stems are many-branched and densely villous. The leaves are simple and opposite, with oblong-lanceolate to oblong-elliptic blades measuring 2.5–10 cm in length and 1.4–4.3 cm in width. The leaf apex is obtuse to rounded, while the base is cordate, occasionally shallow. The surfaces are moderately villous and glandular-dotted, with the hairs on the upper surfaces occasionally somewhat appressed. The margins are coarsely crenate, and the petioles, measuring 0.9–3 cm long, are densely villous. Stipules are absent. The flowers, numbering (6–)8–12 per verticillaster (an inflorescence that resembles a whorl but consists of two crowded cymes on either side of the stem), form in unbranched, terminal, racemose inflorescences that are 8–15 cm long. The pedicels are 1–3 mm long and densely villous. Bracts are oblong-ovate to ovate, with the lowermost pair larger, measuring 20–38 mm long. The calyx is campanulate, 3.5–5 mm long, enlarging in fruit, and is both villous and glandular-dotted. The corolla is white and bilabiate, with a narrow funnelform tube approximately 7–10 mm long and covered in villous and glandular dots. The stamens are four in number, with both pairs of similar length or the upper pair slightly longer. The ovary is superior, 2-carpellate, with basal-axile placentation. The fruit consists of nutlets approximately 1.5–2 mm long, one-seeded, dark green to black, drupaceous, with a fleshy exocarp and an obovoid shape. The seeds are small, lacking endosperm, or scanty and oily. It is found in mesic to wet forests on windward slopes between 700-1,650 meters.