Sleep problems are a commonly reported issue for children and adolescents on the autism spectrum. Given the impact of these problems on the child and their family, it is imperative to provide families with an effective intervention. More recently, research has demonstrated the effectiveness of behavioural interventions informed by functional behavioural assessment (FBA) for treating sleep problems among children and adolescents on the autism spectrum. There is, however, a paucity of research investigating the effectiveness of modification to sleep/wake schedules and other antecedent-based modifications alone, for treating sleep problems in this group. This thesis consists of two parts. Part one is a systematic review of the effectiveness of modification to antecedent variables (including modification to sleep/wake schedules) alone, for treating sleep problems in children and adolescents on the autism spectrum. Part two employed a single-case AB design to investigate the effectiveness of modification to sleep/wake schedules and other antecedent-based modifications alone or in combination, and consequence-based modifications if needed, for reducing sleep problems in children and adolescents on the autism spectrum. This study also examined parental ratings of treatment acceptability; any collateral benefits of behavioural sleep intervention for children’s wellbeing, daytime behaviour, ASD symptomatology, and quality of life, and parents’ sleep, mental health, and relationship quality; and the maintenance of treatment effects. Participants were six children and adolescents aged 3 to 19 years, with a diagnosis of autism spectrum disorder (ASD). Each participant’s individualised intervention was informed by FBA and started with modification to sleep/wake schedules. The results showed that intervention was effective in reducing sleep problems for all participants, and most improvements were maintained at short- and long-term follow-up. Consequence-based modifications only needed to be implemented for one participant to fade sleep dependencies. In this case, modification to sleep/wake schedules were effective in improving the participant’s sleep problems, but a faded parental presence procedure was needed to eliminate parental presence and nighttime milk also needed to be eliminated. Overall, some positive change was evident in children’s wellbeing, daytime behaviour, ASD symptomatology, and quality of life, and in parent’s mental health and sleep following intervention. In addition, all parents indicated that the intervention was acceptable; it was effective, reasonable, and they were willing to implement the strategies. Parents also reported clear understanding though a small number reported that it was costly, disruptive or time consuming, and there were side- effects. Overall, this study indicates the utility of antecedent-based modifications as a less restrictive, minimally sufficient intervention for treating sleep problems among children and adolescents on the autism spectrum.