This species is distinguished from other mountain toucans by its colorful bill: red and black at the tip and yellow-green at the base, where there is a black, thumbprint-shaped mark. The black head is set off from the chestnut-brown back by a pale gray collar. the northern nominate subspecies has dark eyes, while the southern A. h. lateralis has pale eyes. Total length of the gray-breasted mountain toucan is 46–48 cm (18–19 in) long and weight is 244-370 grams (8.6–13.1 oz).
A wide variety of fruits and berries are eaten and this species is often more willing than most largish toucans to leave the canopy to eat raspberries near the base of the trees. They tend to remain quiet while flying and are known to mix often with other birds while foraging, including larger species of tanagers, thrushes and icterids, both behavior unusual in toucans. Very little is known about the life history details for this species.
