Introduction: The transition to primary school appears crucial for a child' s future academic and psychological well-being. Addressing conditions which negatively affect children during this period, such as poor sleep, may improve these outcomes. Sleep problems are common and in a previous efficacy randomised controlled trial, we demonstrated that sleep problems can be identified and improved using school-based screening followed by a brief behavioural intervention. This trial will determine whether the same intervention is beneficial and cost-effective when delivered by an existing school-based health workforce. Methods/design: We will recruit 334 children with sleep problems from approximately 40 schools after screening for behavioural sleep problems in the first year of formal education (Grade Prep). Schools in Melbourne, Australia will be invited to participate from a randomly ordered list of eligible schools and we will approach all caregivers of Grade Prep children. Children who have a parent-reported moderate or severe sleep problem will be randomised into either 'usual care' or 'intervention' groups. Trained nurses from the Primary School Nursing programme will deliver the sleep intervention programme. Intervention: Two to three contacts between the nurse and the parent; initial 45 min face-to-face meeting or phone call, 15 min phone call 2 weeks later and an optional second 30 min face-to-face meeting. Follow-up: 6 and 12 months postrandomisation using parent and teacher surveys and child face-to-face assessments. Primary outcome: child psychosocial functioning at 6 months. Secondary outcomes: child psychosocial functioning at 12 months and child sleep, behaviour, working memory, academic achievement and parent mental health at 6 and 12 months. Cost-effectiveness analysis will compare incremental costs to difference in child psychosocial functioning at 6 months. Registration: International Standard Randomised Controlled Trial Number Register (ISRCTN92448857).