Cyperus hillebrandii var. decipiens is a perennial sedge distinguished by its short, sometimes slightly thickened rhizomes inside brown to reddish brown basal sheaths. Its culms are 15–60(–90) cm tall and 2–6 mm wide near the base. These stems are sharply trigonous and smooth throughout. The leaves are simple, alternate, and linear, with stiff blades measuring (3–)7–12 mm wide. They are as long as or longer than the culms, with entire margins. The lower leaf sheaths are often tinged reddish brown, and stipules are absent. The inflorescences are relatively lax, featuring elongated rays that span 5–18 cm. The spikelets are oblong-lanceoloid in shape, measuring 5.5–6 mm in length, and composed of pale green glumes that are typically tinged pale reddish brown. The glumes measure 3–3.5 mm long. Flowers are bisexual (perfect) and lack petals. Each flower contains three stamens and a superior ovary. The fruit is a trigonous, oblong–ellipsoid achene, measuring 1.2–1.5 mm long and 0.5–0.7 mm wide. Each achene contains a single seed with a thin seed coat that is free from the pericarp. The embryo is basal, and the endosperm is abundant. It is found in ridges, gulches, and stream margins within dry to mesic forests between 360-1,070 meters.