The Sierra Nevada red fox (SNRF), Vulpes vulpes necator, is a high elevation subspecies restricted to montane habitat in California and Oregon. The Sierra Nevada Distinct Population Segment is federally endangered due to low population numbers and low genetic diversity. Despite their recent listing, little is known about their basic ecology, including diet and niche overlap with other mesocarnivores in their community. To help fill these gaps, we used DNA extracted from 924 mesocarnivore scats collected from the Sonora Pass region of the Sierra Nevada to characterize the diets of sympatric SNRFs, coyotes, bobcats, and martens. We used metabarcoding to amplify DNA from food items using chloroplast (trnL) and mitochondrial (12SV5) gene regions to identify plant and vertebrate diet items, respectively. We analyzed data to assess which prey were likely of greatest importance to SNRFs during different seasons and used Pianka's niche overlap index to quantify diet overlap among SNRFs, coyotes, martens, and bobcats. Our results on key prey species, diet diversity, seasonal differences in diet, and dietary overlap with potential competitors provide basic ecological understanding fundamental to recovery planning.