The prominent moth fauna (Lepidoptera: Notodontidae) of Yanayacu Biological Station (Napo Province) in northeastern Ecuador was surveyed to assess which species at the site had been previously described and which were new to science. Taxonomic studies based on comparisons with type material revealed that, of the 67 Notodontidae recorded at Yanayacu, 54% were undescribed before 2009. In this article, 27 species belonging to 12 different genera in four subfamilies are newly described. These findings emphasize the remarkable levels of undocumented insect diversity found in Andean cloud forests, adding further strength to the argument that conservation efforts should focus on preserving such habitats.