Ailanthus vietnamensis is a monoecious tree that can grow 8 meters in height with a diameter at breast height of 20 centimeters. The bark is yellowish-grey and smooth, and the twigs are stout, and are yellowish-green in color. The lenticles are ochre-colored, and the leaf scars are large and heart-shaped. Leaves are spirally arranged pinnately compound leaves up to 45 cm long, and are clustered at the end with 6-10 pair of opposite leaves. The petiole connecting the leaves are 4-11 centimeters long and are puberulous. The leaflets are entire, and are narrow ovate by 5–11 by 1.5-3.5 cm. They are mostly smooth above and are more pubescent beneath. The leaflets are apex acuminate with an obtuse tip, and the lateral nerves are 6-18 pairs. The midrib and lateral nerves are prominent on the underface and are pubescent, and usually have black, round elliptical glands especially on the nerves.[3]
The inflorescences axillary panicles can be up to 19 centimeters long, and can be puberulous to pubescent. The bisexual flowers are up to 1-3 millimeters and the pedicles are densely hairy. The fruit is a samara, which are narrowly elliptic and can be 7–10 by 1.7-2.4 centimeters away from the flower on a slender stalk. Thin wings surround each single flat seed.[3]
