The tricolored bat (Perimyotis subflavus) is widely distributed throughout eastern North America. However, this species has also undergone severe population declines in areas where white-nose syndrome has taken hold. Previous records in Colorado showed what appeared to be vagrant individuals with no evidence of established populations. Herein we provide new records for Boulder and Weld Counties, Colorado. We also provide evidence of reproduction supporting the hypothesis of westward expansion of this species. Because the tricolored bat has been significantly impacted by white-nose syndrome in eastern North America, the Rocky Mountain West may provide at least a temporary refugium from this disease.