The American hazelnut grows to a height of roughly 2.5 to 5 m (8 to 16 ft), with a crown spread of 3 to 4.5 m (10 to 15 ft). It is a medium to large shrub, which under some conditions can take the like of a small tree. It is often multi-stemmed with long outward growing branches that form a dense spreading or spherical shape. It spreads by sending up suckers from underground rhizomes 10 to 15 cm (4 to 6 in) below the surface.

It blooms in very early to mid spring, producing hanging male (staminate) catkins 4 to 8 cm (1+1⁄2 to 3+1⁄4 in) long, and clusters of 2–5 tiny female (pistillate) flowers enclosed in the protective bracts of a bud, with their red styles sticking out at the tip. The male catkins develop in the fall and remain over the winter. Each male flower on a catkin has a pair of bracts and four stamens.

American hazelnut produces edible nuts that mature at a time between July and October. Each nut is enclosed in two leaf-like bracts with irregularly laciniate margins.