Black walnut is highly prized for its wood, which is used to manufacture furniture, wood paneling and veneer and gunstocks. While the fruit of the tree provides food for people and wildlife, the outer hulls have been used for centuries to make tinctures and infusions to address tinea infections of the skin (i.e., ringworm) and for use as an internal vermifuge.

The active compound in black walnut is juglone (5-hydroxy-alphanapthaquinone), which occurs in all parts of the tree. Crushed shells on the ground or contamination in bedding material can produce allergic reactions in horses. Black walnut hulls are also toxic to fish. In fact, Native Americans would toss the hulls into a body of water to stun the fish, making them easy to catch.

Black walnut hulls are also used in several industries. During World War I, they were used like sand blast to clean airplane pistons. The hulls are still used today as a filler in dynamite, as a non-slip agent in tires, and as an additive in products used to clean jet engines. The crushed shells are also found in paint strippers and in certain insecticides.