Peripheral populations are often characterized by small population size and low genetic diversity, with many at risk of extirpation. These characteristics may be even more pronounced in human-modified landscapes that further reduce the resiliency of populations to environmental change. Situated at the northwestern edge of the species’ range, the western American badger (Taxidea taxus jeffersonii) is an endangered mammal in Canada, where it inhabits the interior grassland and open forest ecosystems of British Columbia (BC) and continues to be threatened by severe vehicle-induced mortality rates and other anthropogenic factors. Here, we collected mitochondrial DNA haplotypic and microsatellite genotypic data to investigate the extent and distribution of American badger genetic variation within and among sites in British Columbia, and relative to adjacent populations in the USA, including in Washington state. From these data, we reconstructed population structure and connectivity, and examined current designatable unit status. Patterns of genetic variation for American badgers in British Columbia were as expected for peripheral populations, including reduced genetic diversity, increased population differentiation, and evidence of demographic contraction. Furthermore, we found limited connectivity between regional populations in our study area and identified significant substructure isolating the most northwestern sampling unit (Cariboo), findings that starkly contrast with the high levels of gene flow observed between populations across the species’ range core. These results have important implications for current designatable unit status for western American badgers in British Columbia and emphasize the need for further population monitoring and mitigation of potential barriers to gene flow.