Over 50% of pediatric cancer patients report problems with their sleep, characterized by insomnia disorder symptoms. This results in considerable physical and psychosocial morbidity, including behavioral dysregulation, increased anxiety and depression, obesity, and early diabetes. Despite evidence in general pediatrics demonstrating that preventive parental education interventions are highly effective at improving child sleep and family well-being, there have been no published studies of interventions designed to prevent or reduce this prevalent late effect of cancer therapy. Building on our findings that early on during a child’s cancer treatment, overwhelmed parents employ short-term coping strategies that disrupt long-term sleep, we propose to develop an insomnia prevention program that provides early intervention. Acute lymphoblastic leukemia (ALL) is the most common childhood cancer with overall survival rates of 90% in the context of standardized chemotherapy regimens that are known to disturb sleep. ALL patients thus are an ideal patient population in which to first develop such an intervention given the vast majority will be long-term survivors. Since their lifesaving cancer treatment protocols cannot be altered, how the child and their family respond to these medical disruptions to sleep plays a critical role in how severe acute sleep problems are and how long they persist. Our multi-disciplinary research team will leverage the uniform care delivery setting of the Dana-Farber Cancer Institute ALL Consortium clinical trial Protocol 16-001, including its unprecedented parent-reported socioeconomic status (SES) data, to develop an insomnia-prevention intervention targeted to the specific needs of children living in low-SES households. Our specific aims are to: (1) identify modifiable sleep behaviors in a cohort of pediatric ALL patients during maintenance therapy; (2) develop a preventive insomnia intervention that reduces the negative impact of pediatric ALL treatment on sleep; (3) evaluate the acceptability and feasibility of the novel intervention. We will conduct a single-arm trial of the preventive intervention in a sample of N=30 families of low-SES pediatric ALL patients to determine the acceptability and feasibility of the novel protocol. This will serve as the critical first step to the next step of our goal to conduct a fully powered multi-center trial. Insomnia is a known problem for pediatric cancer patients that often develops during treatment and can persist for decades after cancer therapy has ended. Knowledge from this innovative proposal will shift the current model that insomnia is an expected late effect of treatment for the majority of pediatric ALL patients. We are committed to the clinical care model that “it is better to prevent diseases than to concentrate resources on treating diseases after they become clinically apparent.” By translating evidence into clinical practice for childhood cancer patients, we can significantly improve the health outcomes for children who are already at risk for long-term co-morbidities as a result of their cancer treatments.