Acer negundo is a usually fast-growing and fairly short-lived tree that grows up to 10–25 meters (35–80 ft) tall, with a trunk diameter of 30–50 centimeters (12–20 in), rarely up to 1 meter (3.3 ft) diameter. It often has several trunks and can form impenetrable thickets.
The shoots are green, often with a whitish to pink or violet waxy coating when young. Branches are smooth, somewhat brittle, and tend to retain a fresh green colour rather than forming a bark of dead, protective tissue. The bark on its trunks is pale gray or light brown, deeply cleft into broad ridges, and scaly.
Unlike most other maples (which usually have simple, palmately lobed leaves), Acer negundo has pinnately compound leaves that usually have three to seven leaflets. Simple leaves are also occasionally present; technically, these are single-leaflet compound leaves. Although some other maples (such as Acer griseum, Acer mandshuricum and the closely related A. cissifolium) have trifoliate leaves, only A. negundo regularly displays more than three leaflets.
The leaflets are about 5–10 centimeters (2–4 in) long and 3–7 centimeters (1 1⁄4–2 3⁄4 in) wide with slightly serrate margins. Leaves have a translucent light green color and turn yellow in the fall.
The flowers are small and appear in early spring on drooping racemes 10–20 centimeters (4–8 in) long. The fruits are paired samaras, each seed slender, 1–2 centimeters (1⁄2–3⁄4 in) long, with a 2–3 centimeters (3⁄4–1 1⁄4 in) incurved wing; they drop in autumn or they may persist through winter. Seeds are usually both prolific and fertile.
Unlike most other maples, A. negundo is fully dioecious and both a male and female tree are needed for either to reproduce.