Challenging behaviours often co-occur at high rates among those with autism spectrum disorder and intellectual disability. Challenging behaviours, including self-injury, aggression and property destruction, can be associated with social impairment and increased caregiver demands and stress. These behaviours often arise from and are maintained by a combination of biological and environmental risk factors throughout the lifespan. Given the impact of challenging behaviours on development, function-based assessment and intervention approaches are crucial. The prevalence, risk factors, assessment tools and evidence-based treatment options utilised for individuals with developmental disorders are discussed.