A number of rare birds have their homes on the mountain. Ravens, marsh harriers, buzzards and hobbies breed there as well as snipe, woodcock, short eared owls, sparrowhawks and kestrels.

It is one of the few locations in Ireland and Britain where six of the migratory warblers can be heard in one place. Blackcap, chiffchaff, willow warbler, garden warbler, whitethroat and grasshopper warbler can be heard all over the mountain all summer long.

Wind turbines pose a lethal threat to all birds, but particularly those migrating at night. Sliabh Bán is on the direct northeast-southwest migratory route across Ireland. The density of turbines proposed on the mountain means that very few of the westward migrants would escape the blades. A colony of whooper swans winters on the turloughs at Lisonuffy, to the west of the mountain; it is likely that a wind farm would mean the extinction of this species in the area.

Red deer are present on the mountain in small numbers.

Pine martens, one of Europe's rarest mammals, breed on Sliabh Bán.