Study Design* <p>Systematic review and meta-analysis.</p> Objectives <p>In this study, the effects of the antioxidant melatonin on motor function after spinal cord injury were investigated in preclinical studies.</p> Setting <p>IRAN</p> Methods <p>The search strategy was designed based on keywords related to melatonin and spinal cord injury. The primary screening was based on title and abstract, and the secondary screening was based on the full text of the articles. After extracting data from the articles, statistical analysis was performed using STATA software. Standardized mean differences were used to analyze the results of the included studies. Subgroup analysis and quality control of articles were also performed.</p> Results <p>Based on the results of 29 separate experiments, melatonin showed a significant strong effect compared to the untreated group. The results showed that IP injection and multiple administrations days had the strong effect in the first three days as well as after 3–4 weeks. But more studies are needed to draw conclusions about its longer term effects. The analysis of MDA, SOD and GSH redox factors showed that the amount of MDA decreased and the amount of GSH increased in the treated animals. Also, the inflammatory factors IL-1Β and TNF-α as well as apoptosis and the rate of neuronal cell death, were reduced in animals that received melatonin, while the number of viable neurons was increased in melatonin treated animals.</p> Conclusion <p>Melatonin is an antioxidant supplement, which can be considered for clinical trials in human SCI patients.</p> Sponsorship <p>IRAN University of medical sciences</p>