Greenbrier is a slender, spiny, woody vine climbing by coiled tendrils.
Leaves alternate, simple, 1½–4 inches long, 1¼–3 inches wide, broadly heart-shaped or oval or lance-shaped; margins entire; upper surface dark green, sometimes with lighter blotches; lower surface smooth, conspicuously whitened with a waxy coating or bluish-gray or silvery. There are 3 main veins at the leaf base. Leaf stalk sometimes has a spine on each side at the base. Leaves turn copper-colored in winter, before the leaves drop off.
Stems are slender, climbing by delicate tendrils; tendrils arising in pairs at the base of leaf stalks; young stems smooth, mostly spineless; older stems green to dark brown, smooth; spines sometimes numerous, green to reddish brown or black, about ¼ inch long, straight or slightly curved.
Flowering is in May–June. Flowers are yellowish green, small, smooth; male and female flower clusters on the same plant, arising in the leaf axils of new stem growth; cluster stalk ¼–1¼ inches long and flattened; clusters with 6–12 flowers; petals 6.
Fruits mature September–October. Fruits are shiny black berries, ¼ inch thick, globe-shaped, with a white waxy coating; occur in small, sparse clusters. Seeds 2 or 3 per fruit.