Background and Aims: Melatonin (MT), a naturally occurring pituitary hormone has a sleep promoting effect. There are very few studies on pre-operative oral MT (0.2-0.5 mg/kg) in children. We planned a study to assess the efficacy of oral MT in two doses and compare it with oral midazolam and placebo for pre-operative anxiolysis, sedation, maintenance of cognition and psychomotor skills, parental separation behaviour and venepuncture compliance. Methods: This prospective double-blind randomised study was conducted after ethical committee approval on 100 children aged 5-15 years, American Society of Anaesthesiologists physical status I and II undergoing elective surgery at our hospital from January 1, 2014, to December 31, 2014. Mentally disordered children were excluded from the study. They were randomised into four groups of 25 each (A, B, C, D) to receive either oral MT 0.5 mg/kg or 0.75 mg/kg or oral midazolam 0.5 mg/kg or placebo 45-60 min, respectively, before induction. The child′s anxiety, cognition and psychomotor function before and after pre-medication, behaviour during the parental separation and venepuncture were appropriately scored. Kruskal-Wallis analysis of variance for intergroup and Wilcoxon matched pairs tests for intragroup comparisons of data were applied. Results: The four groups were comparable regarding mean age, weight and sex. The anxiety score reductions in the three groups when compared to placebo were statistically significant. Children receiving MT 0.75 mg/kg had maximum anxiolysis and venepuncture compliance (P < 0.05). Cognition was decreased with maximum sedation, successful parental separation and psychomotor impairment in the midazolam group (P < 0.05). Conclusion: Oral MT (0.5 mg/kg and 0.75 mg/kg) in children decreases pre-operative anxiety without impairing cognitive and psychomotor functions, the 0.75 mg/kg dose being most effective.