Based on data from the Longitudinal Study of Australian Children linked with pharmacy dispensing data from the Australian Government’s Pharmaceutical Benefits Scheme, we calculated the 1-year prevalence of psychotropic medicine supply in children and adolescents with Autism Spectrum Disorder (ASD) as reported by parents in 2014. The majority of children and adolescents with ASD in Australia were not treated with psychotropic medicine. One-third had claims for at least one psychotropic medication, most commonly medications for attention-deficit/hyperactivity disorder (ADHD), and antidepressants. Antipsychotics were supplied to less than one in twenty children and approximately one in ten adolescents. In line with findings from North America, psychotropic medicine was more often supplied to children and adolescents with ASD and comorbid ADHD.