The adult King Vulture is the most strikingly colored of the New World vultures.[17] It is predominantly white, though its ruff, flight, and tail feathers range from gray to an opalescent black.[18] The white plumage also has a slight rose-yellow tinge to it.[19] It has a thick, strong bill that, whilst the most powerful among the New World vultures, is quite small compared to that of other large birds of prey.[17] This bill has a hooked tip and a sharp cutting edge.[18] The bird has broad wings and a short, broad, and square tail.[19] Its eyes are straw-colored and it has keen eyesight.[7] Unlike some New World vultures, the King Vulture lacks eyelashes.[20] The King Vulture also has a highly noticeable yellow fleshy crest on its orange and black bill;[17] this caruncle does not fully form until the bird’s fourth year.[21] It also has gray legs and long, thick claws.[19] The vulture is minimally sexually dimorphic, with no difference in plumage and little in size between males and females.[22] The juvenile vulture has a dark bill and eyes, and a downy, gray neck that soon begins to turn the orange of an adult. Younger vultures are a slate gray overall, and, while they look similar to the adult by the third year, they do not completely molt into adult plumage until they are approximately five or six years of age.[19]

The vulture’s head and neck are featherless as an adaptation for hygiene, though there are black bristles on parts of the head; this lack of feathers prevents bacteria from the carrion it eats from ruining its feathers and exposes the skin to the sterilizing effects of the sun.[23] The skin on the neck and head can be many colors, including yellow, orange, blue, purple, and red.[24] The bird's skin is also wrinkled near the ear and back of the neck.[22]

Excluding the two species of condors, the King Vulture is the largest of the New World vultures. Its overall length ranges from 67–80 centimeters (27–32 in) and its wingspan averages 1.2–1.98 meters (4–6.5 ft). Its weight ranges from 2.7–4.5 kilograms (6–10 lb).[7]