Alzheimer's disease is the most common type of dementia and is responsible for up to 80% of dementia diagnoses and is the sixth leading cause of death in the United States. An estimated 38,000 American Indian/Alaska Native (AI/AN) people aged ≥65 years were living with Alzheimer's disease and related dementias (ADRD) in 2020, a number expected to double by 2030 and quadruple by 2050. Administrative healthcare data from the Indian Health Service (IHS) were used to estimate ADRD among AI/AN populations. Administrative IHS healthcare data from federal fiscal years 2016 to 2020 from the IHS National Data Warehouse were used to calculate the count and rate per 100,000 AI/AN adults aged ≥45 years with at least one ADRD diagnosis code on their medical record. This study identified 12,877 AI/AN adults aged ≥45 years with an ADRD diagnosis code, with an overall rate of 514 per 100,000. Of those, 1856 people were aged 45-64. Females were 1.2 times (95% confidence interval: 1.1-1.2) more likely than males to have a medical visit with an ADRD diagnosis code. Many AI/AN people with ADRD rely on IHS, tribal, and urban Indian health programs. The high burden of ADRD in AI/AN populations aged 45-64 utilizing IHS health services highlights the need for implementation of ADRD risk reduction strategies and assessment and diagnosis of ADRD in younger AI/AN populations. This study provides a baseline to assess future progress for efforts addressing ADRD in AI/AN communities.