Background Aggressive behaviours are common in people with neurodevelopmental conditions, contributing to poorer quality of life and placement breakdown. However, there is limited empirical research documenting the prevalence and persistence of aggressive behaviours in autism. In this longitudinal study, aggressive behaviours were investigated in a sample of autistic individuals over 10 years. Methods Caregivers of autistic individuals, both with and without intellectual disability, completed questionnaires relating to the presence of aggressive behaviours at T1 [N = 229, mean age in years 11.8, standard deviation (SD) 5.9], T2 (T1 + 3 years, N = 81, mean age in years 15.1, SD 5.9) and T3 (T1 + 10 years, N = 54, mean age in years 24.5, SD 8.1). Analyses examined the presence and persistence of aggressive behaviours and the predictive value of established correlates of aggression. Results Aggressive behaviours were common at baseline (61.6%) but only persistent in 30% of the sample over 10 years. Higher composite scores of overactivity and impulsivity at T1 were significantly associated with the persistence of aggressive behaviours at T2 (P = 0.027) and T3 (P = 0.012) with medium effect size. Conclusions Aggressive behaviours are common in autism, but reduce with age. Behavioural correlates of attention deficit hyperactivity disorder (ADHD) predict the presence and persistence of aggressive behaviour and as such may be useful clinical indicators to direct proactive intervention resources to ameliorate aggressive behaviours.