Up to 83% of children with Autism Spectrum Disorder (ASD) experience some form of sleep disturbance involving challenging behaviours. In the treatment of challenging behaviours, there is strong evidence for using interventions informed by Functional Behavioural Assessment (FBA). FBA is used to identify variables that maintain challenging behaviour in order to develop individualised, comprehensive treatments. There is a paucity of research investigating the use of FBA to inform treatments for sleep disturbance in children with ASD, and a lack of evidence-based, effective treatments among such children. This project has four objectives: (1) investigating the use of FBA to develop individualized, comprehensive, parent-implemented treatments for sleep disturbance for children with ASD; (2) measuring the durability of positive treatment effects over time; (3) assessing the impact of successful treatment of sleep problems on parent and child wellbeing and quality of life; and (4) to explore parent perspectives on these treatments.