Mule deer (Odocoileus hemionus) and white-tailed deer (O. viginianus) have been studied extensively as individual species throughout their respective North American ranges. However, comparatively little is known about interactions between these closely related species where they occur sympatrically. We studied spatial and habitat use patterns of sympatric mule deer and white-tailed deer at 3 hierarchical scales on Rocky Mountain Arsenal (RMA), Colorado, USA using radiotelemetry. Similarities in annual spatial distribution analyses (coarse scale) and diet composition analyses (fine scale) suggested the 2 species may have been competing for space and forage on RMA. However, seasonal differences in habitat use patterns resulted in spatial segregation, thereby allowing the 2 species to coexist. Mule deer used habitats primarily based on forage availability and secondarily for cover. White-tailed deer used habitats primarily based on availability of security cover. Habitat management and restoration efforts should consider maintaining existing composition and juxtaposition of vegetation associations that allow species to maintain seasonal allopatric distributions and, subsequently, coexistence. Increased deer population levels may lead to increased interactions between species.