IMPORTANCE: Children with neurodevelopmental disorders have a higher prevalence of sleep disturbances. Currently there is variation in the use of melatonin; hence, an up-to-date systematic review is indicated to summarise the current available evidence. OBJECTIVE: To determine the efficacy and safety of melatonin as therapy for sleep problems in children with neurodevelopmental disorders. DATA SOURCES AND STUDY SELECTIONS: PubMed, Embase, the Cumulative Index to Nursing and Allied Health Literature and the Cochrane Central Register of Controlled Trials were searched from inception up to January 2018. Two reviewers performed data assessment and extraction. We assessed randomised controlled trials that compared melatonin with placebo or other intervention for the management of sleep disorders in children (<18 years) with neurodevelopmental disorders. DATA EXTRACTION AND SYNTHESIS: We identified 3262 citations and included 13 studies in this meta-analysis. MAIN OUTCOMES: Main outcomes included total sleep time, sleep onset latency, frequency of nocturnal awakenings and adverse events. RESULTS: Thirteen randomised controlled trials (n=682) met the inclusion criteria. A meta-analysis of nine studies (n=541) showed that melatonin significantly improved total sleep time compared with placebo (mean difference (MD)=48.26 min, 95% CI 36.78 to 59.73, I CONCLUSION: Melatonin appeared safe and effective in improving sleep in the studied children. The overall quality of the evidence is limited due to heterogeneity and inconsistency. Further research is needed.