Despite the presence of mostly endemic species, the most comprehensive data set on the distribution and ecology of small mammals inhabiting Simien Mountains National Park (SMNP) dated from 1927. The study we carried out and report here provides a unique opportunity to assess the possible role of climate change over the last 88 years on the elevational distribution of mammals in the Ethiopian highlands. Between September and November 2015, three of us (EWC, WTS, YM) collected nonvolant small mammals at four sites (2,900, 3,250, 3,600, and 4,000 m a.s.l.) along the western slope of the Simien Mountains using standardized sampling. Over a 4-week period we recorded 13 species, comprising 11 species of rodents and two of shrews, all endemic to the Ethiopian Plateau. We found the greatest species richness at mid-elevations (3,250 m), consistent with a general pattern found on many other mountains worldwide, but less so in Africa. We compared our species distribution results to the 1927 data set and found upward elevational shifts in species' ranges, highlighting the role and influence of climate change on the small mammal community. SMNP represents an exceptionally valuable core area of endemism and the best protected natural habitat in northern Ethiopia.