Objective Characteristics of older people with and without dementia who are hospitalised following self‐harm remains largely unexplored. This research compares the characteristics of older people with and without dementia who self‐harm, compares associations of mental health‐related diagnoses with those hospitalised for a self‐harm and a non‐self‐harm injury and examines mortality by injury intent. Method A population‐based study of individuals aged 50+ years with and without dementia admitted to hospital for a self‐harm injury (and those with other injuries) using linked hospital admission and mortality records during 2003–2012 in New South Wales (NSW), Australia. Health outcomes, including hospital length of stay (LOS), 28‐day readmission and 30‐day and 12‐month mortality were examined by dementia status. Results There were 427 hospitalisations of individuals with dementia and 11,684 hospitalisations of individuals without dementia following self‐harm. The hospitalisation rate for self‐harm for individuals with dementia aged 60+ years was double the rate for individuals without dementia (72.2 and 37.5 per 100,000). For both older people with and without dementia, those who self‐harmed were more likely to have co‐existent mental health and alcohol use disorders than individuals who had a non‐self‐harm injury. Individuals with dementia had higher 12‐month mortality rates, 28‐day readmission and longer LOS than individuals without dementia. Conclusion Dementia is associated with an increased risk of hospitalisation for self‐harm in older people and worse outcomes. The high rate of coexistent mental health conditions suggests that interventions which reduce behavioural and psychological symptoms of dementia might reduce self‐harm in people with dementia. Copyright © 2016 John Wiley & Sons, Ltd.