A distinctive new species of sturnirine bat, Sturnira (Sturnira) koopmanhilli, new species (Chiroptera: Phyllostomidae: Stenodermatinae), is described from 49 specimens collected in the Pacific drainage of the western Andes, at 300–2000 m in western Ecuador and Colombia. This yellow-shouldered bat is endemic to this Chocoan region where it is known from nine localities in Ecuador (Esmeraldas and Chimborazo) and Colombia (Chocó, Valle del Cauca, and Nariño). This moderately large Sturnira species (forearm length, 48.1–52.4 mm) is compared with Sturnira mordax (Goodwin, 1938) (forearm length, 43.0–49.2) and Sturnira ludovici Anthony, 1924 (forearm length, 43.9–49.5). Salient characters that distinguish the new species from these two cogeners include a bicolored appearance of dorsal fur, recessed hypoglossal foramina, presence of a sulcus on posterior faces of upper canines, and teeth P2 > M2. Teeth I1 and i1 are protrudent and robust, which set the new species apart from other Sturnira species. Spacing between teeth P1-M3 and p1-m3 is present in the new bat and with the subgenus Corvira. The new species is placed in the subgenus Sturnira.