Purpose Older adults living in rural areas may face barriers to obtaining a diagnosis of Alzheimer's disease and related disorders (ADRD). We sought to examine rural‐urban differences in prevalence of ADRD among Medicare beneficiaries in Kentucky and West Virginia, 2 contiguous, geographically similar states with large rural areas and aged populations. Methods We used Centers for Medicare and Medicaid Services Public Use Files data from 2007 to 2013 to assess prevalence of ADRD at the county level among all Medicare beneficiaries in each state. Rural‐Urban Continuum Codes were used to classify counties as rural or urban. We used Poisson regression to estimate unadjusted and adjusted prevalence ratios. Primary analyses focused on 2013 data and were repeated for 2007 to 2012. This study was completely ecologic. Findings After adjusting for state, average beneficiary age, percent of female beneficiaries, percent of beneficiaries eligible for Medicaid in each county, Central Appalachian county, percent of age‐eligible residents enrolled in Medicare, and percent of residents under age 65 enrolled in Medicare in our adjusted models, we found that 2013 ADRD diagnostic prevalence was 11% lower in rural counties (95% CI: 9%‐13%). Conclusions Medicare beneficiaries in rural counties in Kentucky and West Virginia may be underdiagnosed with respect to ADRD. However, due to the ecologic design, and evidence of a younger, more heavily male beneficiary population in some rural areas, further studies using individual‐level data are needed to confirm the results.