INTRODUCTION: We investigated the incidence of diagnosed dementia and whether age at diagnosis and survival afterward differs among the United Kingdom's three largest ethnic groups. METHODS: We used primary care electronic health records, linked Hospital Episode Statistics and mortality data for adults aged ≥65 years. We compared recorded dementia incidence 1997-2018, age at diagnosis, survival time and age at death after diagnosis in White, South Asian, and Black people. RESULTS: Dementia incidence was higher in Black people (incidence rate ratios [IRR] 1.22, 95% CI 1.15-1.30). South Asian and Black people with dementia had a younger age of death than White participants (mean difference for South Asian participants -2.97 years, (95% CI -3.41 to -2.53); and Black participants -2.66 years, (95% CI -3.08 to -2.24). DISCUSSION: South Asian and Black peoples' younger age of diagnosis and death means targeted prevention and care strategies for these groups should be prioritized and tailored to facilitate take-up.