Zinnia peruviana is an annual plant up to 50 cm tall (rarely 100 cm tall). The stems are green, but later become yellow or purple. The leaves are ovate, elliptic or lanceolate, 2.5–7 cm long and 8–3.5 cm wide; 3- to 5-nerved. The peduncles are 1–7 cm long. Flower heads with 6–21 red, maroon or yellow ray florets (with a 0.8–2.5 cm long petal each) surrounding 12–50 yellow disc florets (with 0.1 cm long corolla lobes). Fruits (cypselae) oblanceolate to narrowly elliptic, 0.7–1 cm long, 3-angled or compressed, striate.