The objective was to describe mental health service and psychotropic medicine use among a cohort of Aboriginal young people and quantify their relation to sociodemographic, family and health factors. In a prospective cohort study with data linkage, 892 Aboriginal children aged 0-17 years living in urban and regional areas of New South Wales, Australia, were included. We assessed mental health-related service use, paediatric service use and psychotropic medicine dispensing claims covered by the Australian Government Medicare Benefits Schedule and the Pharmaceutical Benefits Scheme from July 2012 to June 2017. Most children (71%) did not have a record of mental health service or psychotropic medication use. 18.7% had ⩾1 mental health-related service claim; 26.7% had ⩾1 paediatric service claim; and 20.3% had ⩾1 psychotropic medicine dispensing claim. General practitioner services were the most accessed mental health-related service (17.4%) and 12.7% had been dispensed attention-deficit hyperactivity disorder medicines. Child characteristics associated with treatment included emotional and behavioural problems (prevalence ratio: 1.97, 95% confidence interval = [1.46, 2.64] for mental health services; prevalence ratio: 2.87, 95% confidence interval = [2.07, 3.96] for medicines) and risky behaviour (prevalence ratio: 1.56, 95% confidence interval = [1.12, 2.16] for mental health services; prevalence ratio: 2.28, 95% confidence interval = [1.54, 3.37] for medicines). Parent-related factors included chronic illness (prevalence ratio: 1.42, 95% confidence interval = [1.03, 1.95] for mental health services; prevalence ratio: 2.00, 95% confidence interval = [1.49, 2.69] for medicines) and functional limitations (prevalence ratio: 1.61, 95% confidence interval = [1.16, 2.24] for mental health services; prevalence ratio: 1.86, 95% confidence interval = [1.34, 2.59] for medicines). Most Aboriginal children and young people did not have claims for mental health services or medicines. Aboriginal children with emotional and behavioural problems, or parents with health problems were more likely to have mental health service or medicine claims.