[4] Two subspecies are recognized, the nominate: The grey-breasted mountain toucan is 41 to 48 cm (16 to 19 in) long and weighs 244 to 370 g (8.6 to 13 oz).

The nominate subspecies has a bright yellow rump, pale gray-blue flanks, chestnut thighs, and red undertail coverts.

[5] The nominate subspecies of grey-breasted mountain toucan is found from central and southern Colombia into eastern Ecuador.

[5] The grey-breasted mountain toucan forages from near the ground up to the forest's canopy, singly, in pairs, or in small groups that might be extended families.

[5] The grey-breasted mountain toucan's breeding season spans from December to February in Colombia and from June or July to November in Ecuador and Peru.

[1] Though it occurs in some protected areas and is thought to be locally common, "[p]opulation fragmentation and inbreeding are possible problems".