Bidens cosmoides is a scandent, suffrutescent perennial herb that grows between 1 and 2.5 meters tall, with spreading branches that sometimes take root. Its leaves are pinnately compound, typically 9–33 cm long, including the petiole. The leaflets range from 3 to 9 in number and are lanceolate to ovate-lanceolate, usually measuring 4–14 cm long and 1.5–6 cm wide. The leaf surfaces are sparsely pubescent, with serrate and ciliate margins. The flowers are in cymes of 1–3 heads, terminating lateral branches only. Each head is pendant and campanulate, measuring 5–8 cm in diameter, including the ray florets. Peduncles are 5.5–15 cm long and sparsely pubescent. The outer involucral bracts are foliaceous, 15–25 mm long, with ciliate margins, while the inner bracts are distinct. The ray florets number between 7 and 19 per head and are sterile, with yellow rays that are 30–52 mm long and 10–15 mm wide. The disk florets number between 12 and 50 per head and are perfect, with a reddish-orange corolla tube and dark yellow lobes. The anthers are black, 4–6 mm long, and exserted beyond the corolla tube. The styles are long, extending 10–30 mm beyond the anthers. The pappus consists of two awns up to 1 mm long or is sometimes absent. The fruits are dark brown achenes that are irregularly curved or contorted, wingless, and measure 8–14 mm long and 1–2 mm wide. They are setose and enveloped by the subtending chaffy receptacular bract. It is found in wet forests between 700-1,200 meters.