Sicyos maximowiczii is a trailing or climbing annual herb. Its stems can extend up to 10 meters long and are about 4 mm in diameter. They display sparse hirsute to glabrate characteristics. The leaves are simple and alternate, with blades reniform to broadly ovate–cordate and feature a narrow to broad basal sinus. These blades range from 6–12 cm long and 6–15 cm wide and are 5–7–angled to shallowly lobed. The apex of each leaf is short-acuminate. The leaf surfaces are initially more or less tomentose, becoming scabrid on the upper surface; the lower surfaces are more densely scabrid or hispid with white hairs. The leaf margins are minutely denticulate. Petioles are stout, ranging from 4–15 cm in length, and hispid. It lacks stipules but has tendrils in the stipular position that are 3–5–branched, aiding in its climbing habit. The flowers are typically unisexual, with the plant being either monoecious or dioecious, and display actinomorphic (radial) symmetry. Staminate (male) flowers are arranged in glandular pubescent panicles 5–23 cm long, with peduncles measuring 2–14 cm and pedicels 2–7 mm long. The pistillate (female) flowers, number 10–25 per head, are sessile and sit on glandular pubescent peduncles (8–)12–40 mm long. The calyx consists of 5 sepals inserted on a hypanthium. The corolla of staminate flowers is pale yellow or white, 5-lobed, about 7–9 mm in diameter, and glandular, with petals usually connate at the base. Staminate flowers contain (2)3(–5) stamens inserted at the base of the hypanthium, with filaments fused into a column and anthers that are curved or flexuous, coherent and spreading, and open by longitudinal slits. Pistillate flowers have no staminodes and feature an inferior ovary, which is 3-carpellate with carpels connate into a single 3-lobed cell; the ovule is single with parietal placentation, and the stigma is 3-lobed with reflexed lobes. The fruit is pale brown and obovoid, measuring 6–12 mm long and 6–9 mm in diameter. It has obscure ribs and densely pilose outgrowths with pale, multicellular, glandular hairs. Each fruit contains one ovate seed, lacking endosperm. It inhabits herb communities alongside plants like Ipomoea indica and Tribulus cistoides or in Scaevola sericea shrubland, typically found on coral sand at sea level.