Lysimachia scopulensis is a branching shrub with stems reaching up to 75 cm long, displaying a red or green coloration and a pulverulent texture when young. The leaves are simple and alternate, spaced (0.5)2–7(8) mm apart, with oblanceolate or sometimes narrowly obovate blades. These blades are coriaceous, almost succulent, and contain internal glands, measuring (33)55–65(86) mm in length and (5)8–11(23) mm in width. The tips of the leaves are slight to extremely recurved, and the apex is attenuated while the base is acute. The upper surfaces of the leaves are dark green, drying to olive green, and are glabrous and pulverulent when young, whereas the lower surfaces are dark green, drying lighter than above, and also glabrous. The flowers are solitary in leaf axils, perfect, (5)6(7)-merous, and campanulate. The pedicels are 20–45 mm long, erect, and green. The calyx comprises five sepals with green or red lobes at the base, scarious margins, and a pulverulent yet glabrous texture. The corolla lobes are red and obovate, measuring 10–11 mm long and 6–7 mm wide. The filaments are 5 mm long, anthers are 2 mm long. It produces globose capsules as fruit, measuring 6.5–7.5(9) mm in size. The seeds are dark brown, irregularly shaped, and measure 2.0–2.5 mm long. It is found on cliffs within diverse lowland mesic forests in the upper Kalalau Valley between 780–880 meters.