OBJECTIVE: To evaluate the feasibility and helpfulness of a behavioral sleep program for children with ADHD, and explore the impact of different program dosages on child and family outcomes. METHODS: Randomised trial comparing a brief (1 session, n=13) and extended (2-3 sessions, n=14) sleep program in children with ADHD (aged 5-14 years) and at least one behavioral sleep disorder (American Academy of Sleep Medicine Criteria). Outcomes included helpfulness and use of interventions, child sleep (parent-reported sleep problem; Child Sleep Habits Questionnaire), ADHD symptoms (ADHD IV Rating Scale), daily functioning (Daily Parent Rating of Evening and Morning Behavior), quality of life (Pediatric Quality of Life Inventory), and caregiver mental health (Depression Anxiety Stress Scales). RESULTS: Twenty-seven families (63% of those eligible) took part. Most parents would recommend the program to others (95%) and found the strategies helpful. Five months post-randomisation, 67% of parents in both groups reported that their child's sleep problems had resolved. Child quality of life, daily functioning, and parental anxiety also improved in the extended group only (Cohen's d: 0.39, 0.47 and 0.50, respectively). There was minimal change in ADHD symptom scores from baseline to 5 months in either group. CONCLUSIONS: A behavioral sleep intervention in children with ADHD is feasible to deliver and improves child sleep by parent report. The extended program resulted in greater improvements in child and caregiver outcomes.