Insomnia is common in autism and associated with challenging behavior and worse parent sleep. Cognitive behavioral treatment for childhood insomnia (CBT-CI) is efficacious in typically developing children, but not yet tested in school-aged children with autism. This single arm pilot tested 8-session CBT-CI in 17 children with autism and insomnia (M age = 8.76 years, SD = 1.99) and their parent(s) (M age = 39.50 years, SD = 4.83). Treatment integrity was assessed for each session [delivery (by therapist), receipt (participant understanding), and enactment (home practice)]. Children and parents wore actigraphs and completed electronic diaries for 2-weeks to obtain objective and subjective sleep onset latency (SOL), total sleep/wake times (TST/TWT), and sleep efficiency (SE) at pre/post/1-month follow-up. Parents also completed the Aberrant Behavior Checklist [irritability, lethargy, stereotypy, hyperactivity, inappropriate speech (e.g., excessive/repetitive, loud self-talk)] at pre/post/1-month. Fifteen children completed all sessions. Average integrity scores were high [90%-delivery/receipt, 87.5%-enactment]. Parents found CBT-CI helpful, age-appropriate, and autism-friendly. Paired samples t-tests (family-wise error controlled) found CBT-CI improved child sleep (objective SOL-18 min, TWT- 34 min, SE-5%; subjective SOL-29 min, TST-63 min, TWT-45 min, SE-8%), and decreased irritability, lethargy, stereotypy, and hyperactivity. At 1-month, objective TST improved, inappropriate speech decreased, but hyperactivity was no longer decreased. Other gains were maintained. Parent sleep (objective SOL-12 min, TST-35 min, TWT-21 min, SE-4%; subjective SOL-11 min, TWT- 31min, SE-11%) and fatigue also improved. At 1-month, gains were maintained. This pilot shows CBT-CI is a feasible treatment that holds promise for improving child and parent sleep and functioning and suggests a randomized controlled trial in school-aged children with autism is worth conducting. Autism Res 2020, 13: 167-176. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Insomnia is common in autism and associated with challenging behaviors and poor parent sleep and stress. Cognitive behavioral treatment for childhood insomnia (CBT-CI) has not been tested in school-aged children with autism. This pilot study shows therapists, parents, and children were able to use CBT-CI to improve child and parent sleep, child behavior, and parent fatigue. Parents found CBT-CI helpful, age-appropriate, and autism-friendly. CBT-CI holds promise for treating insomnia in school-aged children with autism and deserves further testing.