Solanum incompletum is a shrub that can grow up to 3 meters tall, characterized by prominent reddish prickles 3–5 mm long that are laterally flattened at the base and may be absent from the inflorescence. It can be pubescent with yellowish stellate hairs and possesses an intraxylary phloem. The stems feature scattered to abundant prickles. The leaves are simple, alternate, and ovate–elliptic to elliptic in outline, measuring 10–15 cm in length and 6–8 cm in width, though sizes can vary. The leaves have an acute to acuminate apex, a rounded and oblique base, and are often armed with prickles, especially on the lower surfaces and veins. The leaf margins are deep to shallowly lobed, with 1–4 lobes per side, and the veins are prominent on the lower surface. The numerous flowers are arranged in compound, subpaniculate, racemose cymes with up to five branching orders and leaf-opposed. The flowers are bisexual (perfect) and actinomorphic (radially symmetric), with a deeply lobed calyx and a white, broadly stellate corolla approximately 2 cm in diameter. It has (4)5 stamens with short filaments and arcuate, elliptic-oblong anthers that open by terminal pores. The fruit is a berry that may mature from yellowish orange to black, measuring 1.3–1.8 cm in diameter or possibly larger. The seeds are compressed, with a curved embryo and submarginal placement, and endosperm is present. It is found in dry to mesic forests, diverse mesic forests, and subalpine forests between 600-2,020 meters.