The small mammal fauna from northwestern Chubut Province (Argentina) is poorly known. We herein report small mammal assemblages from three new localities: Sierras de Tecka, an extra-Andean system elevated 900 m.a.sl.; Estancia La Mimosa on the Tecka river valley (at ca. 650 m.a.sl.); and Arroyo Pescado (at ca. 620 m.a.sl.) 40 km north of the other sites. Specimens were recovered from disaggregated owl pellets. Total species richness includes 16 native (13 sigmodontine and two caviomorph rodents, and one marsupial) and one introduced species. Estancia La Mimosa had the highest richness (n = 14), while Arroyo Pescado the lowest (n = 11). Four species were only recorded at Estancia La Mimosa (Akodon iniscatus, Calomys musculinus, Oligoryzomys longicaudatus and Mus musculus), two in Sierras de Tecka (Notiomys edwardsii and Microcavia australis) and one in Arroyo Pescado (Geoxus valdivianus). This work also adds new localities for Akodon iniscatus, Geoxus valdivianus, Lestodelphys halli and Notiomys edwardsii in western Chubut Province.