Objective: To estimate the prevalence and incidence of dementia in Northern Territory Indigenous and non-Indigenous populations. Design, setting and participants: Four data sources were used to identify clients with a diagnosis of dementia, from 1 January 2008 to 31 December 2011. The data sources included hospital admissions, aged care services, primary care and death registration. A capture-recapture method was used to estimate prevalence and incidence, including both diagnosed and unknown cases. Main outcome measures: Prevalence and incidence of dementia among the NT Indigenous and non-Indigenous populations. Results: In 2011, the estimated prevalence in the NT Indigenous population aged 45 years and over was 3.7 per 100, and 1.1 per 100 in the corresponding NT non-Indigenous population. The age-adjusted prevalence for the NT Indigenous population was 6.5 per 100, compared with the NT non-Indigenous prevalence of 2.6 per 100, which was similar to the national rate. The prevalence rate ratios of NT Indigenous to NT non-Indigenous men and women, respectively, were: 6.5 and 5.5 for the 45-64-years age group, 4.0 and 4.1 for those aged 65-74 years and 2.1 and 1.9 for those aged 75 years and over. The age-adjusted incidence among the NT Indigenous population aged 45 years and over (27.3 per 1000 person-years) was higher than that among the NT non-Indigenous population (10.7 per 1000 person-years). Conclusion: The NT Indigenous population has a much higher prevalence and incidence of dementia and younger onset of disease compared with their non-Indigenous counterparts. The results highlight the urgent need for interventions to moderate the emerging impact of dementia in the Australian Indigenous population.