It is endemic to Peru and is only known from its type locality near Balzapata, upper Chiriaco River, in the Department of Amazonas.

The iris is silvery gray with greenish cast; the palpebrum has light white reticulation.

[2] Callimedusa duellmani is known from cloud forest at elevations of 1,850–1,910 m (6,070–6,270 ft) above sea level.

[1][2] The type series was collected at night on vegetation overhanging a water-filled ditch along a road.

[2] Potential threat to this poorly known species is agricultural activity in the area of the type locality.