The helmeted hornbill is the largest of the hornbills and is named for the helmet-like protrusion on the upper half of its beak. This casque is a solid block of ivory-like substance and quite unlike the casque of other hornbills, which are typically hollow. The beak of the helmeted hornbill is red and yellow.

They have dark feathers on the wings and most of the body but there is a featherless patch of leathery skin on the neck, which is a reddish brown in males and turquoise in females. They have extremely long central tail feathers (up to a metre long) which are white with dark bands.

Both males and females of this species have horns. Females’ horns are rarely longer than 33cm, whereas adult males' horns are far more striking. At up to 127 centimetres long, they curve upwards and backwards from the head in an arc shape