Sicyos albus is an annual vine that can grow up to 20 meters long. The stems are puberulent, glabrate, and marked with black spots. The leaves are simple and alternate, with broadly ovate-cordate blades featuring a broad basal sinus. They measure 7–11 cm long and 9–12 cm wide and can be shallowly to deeply 3–5-lobed. The deeply lobed specimens have narrowly ovate lobes and contracted at the base, with coarsely dentate to lobulate margins. The leaf apex is acuminate, and the blades are discolorous with denticulate margins. The leaves are petiolate, and the stipules are absent; tendrils in the stipular position are 2-branched. The flowers are usually unisexual, with the plants being monoecious or dioecious and actinomorphic (radially symmetric). The staminate flowers are arranged in panicles 3–7 cm long, with peduncles 2.5–3.7 cm long and pedicels 2–4 mm long, glabrous. The pistillate flowers are 2–8 per head, sessile on peduncles 1–3.5 cm long. The calyx has five sepals inserted on the hypanthium. The corolla of the staminate flowers is white, 5-lobed, ovate, 2–2.5 mm long, glandular-dotted, acute, with petals inserted on the hypanthium alternate with calyx lobes, usually connate at the base, and the limb often rotate. The corolla of the pistillate flowers is white, 4-lobed, with lobes 1.7–2 mm long. Staminate flowers have 2 to 5 stamens inserted at the base of the hypanthium, with filaments connate into a column and anthers that are curved or flexuous, coherent, and twisted in a head, opening by longitudinal slits. Pistillate flowers have staminodes absent and an inferior ovary of a single carpel or 3-carpellate with carpels connate into a single 3-lobed cell, with ovule placentation parietal, and a stigma that is 2-lobed with lobes ca. 1 mm long. The fruit is white, fleshy, and ellipsoid, measuring 29–32 mm long and 10–11 mm in diameter, glabrous, and indehiscent. There is one seed per fruit, ovate, and ca. 13 mm long, with endosperm absent. It is found in wet forests on windward slopes between 1,000-1,600 meters.