It is endemic to the Ecuador and only found in the forests surrounding a small crater lake on the eastern slopes of Sumaco, a volcano in the Napo Province.

[1][2][3] Osornophryne sumacoensis females measure about 32.5 mm (1.28 in) in snout–vent length (mean of three individuals).

The back and limbs are blueish-black, but the belly is blue with black spots.

[1] Osornophryne sumacoensis inhabits the cloud forest surrounding the lake, at 2,500–2,800 m (8,200–9,200 ft) asl.

Volcanic eruption is a threat to this species restricted to a single location.