Mycopteris attenuatissima is restricted to the Chocó region along the western flank of the Andes in Colombia and Ecuador. It is similar to M. alsopteris and often misidentified as that species, but differs by having setose pinna margins. This collection was found growing as an epiphyte which is typical of plants found at middle elevations (1700–2500m). Plants growing above 2500m are typically terrestrial.