In 2008 a mammal survey was conducted in humid tropical forest on the western slope of the Andes near the town of Santa Rosa. Sherman traps, tomahawk traps, pitfall traps, and mist nets were used to collect mammal specimens at two sites (450 m elevation and 702 m elevation). A total of 113 specimens of 32 species were collected from the survey area. Seventeen Chiropteran species (Saccopteryx bilineata, Anoura fistulata, Glossophaga soricina, Micronycteris megalotis, Phyllostomus discolor, Carollia perspicillata, Sturnira bogotensis, Sturnira luisi, Artibeus jamaicensis, Dermanura rava, Dermanura rosenbergii, Platyrrhinus vittatus, Vampyriscus nymphaea, Vampyressa thyone, Eumops auripendulus, Eptesicus innoxius, and Myotis albescens) and one rodent species (Sigmodontomys aphrastus) represent new records for southwestern Imbabura. New elevation records also were documented for Anoura fistulata and Sturnira bogotensis. Shannon diversity analyses of the Chiropteran fauna and overall mammal diversity indicated greater diversity at the 450 m site.