Bumble bees (genus Bombus) are critical pollinators—providing the necessary ecological services for food and crop production. In western North America, species-rich bumble bee communities inhabit mountain ranges. However, as climate change increases temperatures, montane populations are restricted to higher elevations and their ability to disperse and maintain genetic diversity decreases as suitable habitat connecting populations decreases. This genetic isolation could lead to the extirpation of local pollinator populations and a loss of genetic diversity for pollinator species. We analyzed the genetic diversity of four broadly sympatric species of bumble bees with differing elevational niches—Bombus flavifrons, B. melanopygus, B. mixtus, and B. sylvicola—across the Rocky and Cascade Mountains of western North America to assess range-wide population genetic structure. We used microsatellite markers to assess genetic differentiation among populations (F_ST) and performed Bayesian clustering analyses to identify genetic groups within each study species. Further, we investigated if observed genetic differentiation within study species were better explained by isolation by distance (IBD) or isolation by resistance (IBR) by incorporating habitat suitability models (HSMs) into population structure analyses. Although we expected range-wide genetic differentiation for species with more narrow niche requirements, we found evidence of this differentiation for all four study species, with western populations experiencing significant genetic structure relative to inland populations. Additionally, IBR predicted genetic structure better than IBD for B. flavifrons and B. mixtus. Our results suggest that considering habitat connectivity across the geographic range of montane bumble bee species is important for understanding their population structures.