In this study we present the results of inventory efforts of non-volant mammals in Sangay National Park (SNP), one of the least studied regions of Ecuador. We conducted inventories at 9 locations between December 2010 and June 2015 along a gradient of elevations between 1.300 and 3.650 m. To document the presence of non-volant mammals we used capture techniques (Sherman, Tomahawk, and pitfall traps) and direct and indirect detection techniques (track and sign surveys, interviews). The trap effort consisted of 5.730 trap/nights. We detected 86 species in the study area of which rodents were the most diverse group with 36 species (41.8%). The small mammals Chilomys instans, Neusticomys vossi, Ichthyomys cf. stolzmanni, Thomasomys fumeus, Dactilomys dactylinus and Echimys saturnus, the marsupial Marmosa rubra were detected in the SNP for the first time. The shrew-opossum Caenolestes sangay, shrew Cryptotis montivaga and rodents Phyllotis haggardi, Thomasomys fumeus, T. hutsoni, T. cf silvestris, Rhipidomys sp. nov., y Cavia patzelti are endemic species that speak to the biogeographic importance of SNP. Our results with additions from other published studies indicate the presence of 103 species of non-volant mammal, positioning it as the most diverse natural area in the Andes of Ecuador, and as the second most diverse of the tropical Andes.