The snake's body is slender, its head is small and flat, and its tail is short. Scales are smooth but not glossy. Coloration is typically gray or black, with a brownish head and a gray-white or pinkish underside. When the cobra adopts a threat posture by raising its body and flattening its neck into a hood, one or two broad black bands are visible across the throat and inner hood.

Active from dusk to morning, the snake usually spends this time near water. Its diet is quite varied. Small mammals, birds, snakes, lizards, frogs, eggs, and fish are taken. Its venom is potentially lethal to humans, but it does not usually bite people unless cornered or seriously provoked. Sometimes it feigns death. Its notorious spitting, though swift and aggressive, is used for the purpose of making a fast retreat. Its hollow fangs have openings at the front instead of the tip, so that venom is channeled outward rather than downward. Raising its snout, the snake deliberately aims at the eyes of its opponent, and squeezes its venom-gland muscles while forcefully expelling air in a hiss. A spray of venom that reaches the face of the victim can cause temporary blindness. Permanent blindness can result if the eyes are not promptly washed. The venom is harmless on unbroken skin.

Females lay clutches of about 10 to 30 eggs. Hatchlings average 12 inches (30 centimeters) and can spit venom at birth. Other Naja cobras spit on occasion, but only the black-necked cobra and the ringhals snake (Hemachatus, a cobra of southern Africa), are fully adapted for spitting. (See also Cobra.)