BACKGROUND: Anxiety and sleep disorders are prevalent problems in patients presenting with ST-segment-elevation myocardial infarction (STEMI). Usually, these problems are managed by benzodiazepines, which-albeit effective-could cause adverse effects and drug interaction. OBJECTIVE: This study was designed to compare the effects of melatonin and oxazepam in the management of anxiety and insomnia on patients following primary percutaneous coronary intervention (PCI) with a view to providing a safer alternative. METHODS: This study was designed as a randomized clinical trial. STEMI patients managed with primary PCI were enrolled and randomized into 2 groups through the permuted block randomization. The patients received either oxazepam (10 mg) or melatonin (3 mg) every night. Autoimmune disease or previous use of psychoactive medications was considered the exclusion criterion. Levels of anxiety and sleep quality were evaluated using the Hamilton Anxiety Rating Scale (HAM-A) and the Groningen Sleep Quality Score and compared between the groups. RESULTS: Each group contained 20 patients. Melatonin showed a significant advantage over oxazepam in improving sleep quality ( P = 0.040). Comparisons of the efficacy of both medications in lowering the anxiety levels when considering all the items of the HAM-A, including those related to cardiovascular disease, were significantly in favor of melatonin ( P = 0.019). CONCLUSIONS AND RELEVANCE: The results of this study suggest that melatonin, a drug with more favorable drug interaction and adverse effect profile, could be more effective than oxazepam in improving the sleep quality and anxiety levels of patients presenting with STEMI, and it could be considered a new alternative to benzodiazepines in this setting.