Ferocactus johnstonianus is a solitary, spherical to short cylindrical cactus that can grow over 1 meter tall and up to in diameter. It has 24 to 31 slightly humped ribsand 22 to 25 golden-yellow, awl-shaped spines that turn brown with age and reach up to long, without differentiating into central and radial spines. The cactus produces funnel-shaped yellow flowers that grow up to long and in diameter. Its fruits, which are about long, sometimes open with a basal pore.