The aim of this study is to evaluate the possible protective effects of melatonin on hemostatic parameters in diabetic rats. For this purpose, 32 adult, male, healthy Wistar Abino rats were seperated into four groups. Control group didn't exposure any trial. Melatonin group was treated with 50 mg/kg melatonin by intraperitoneally during 8 weeks. In diabetes group, diabetes was induced by subcutaneous injections of streptozotocin at dose of 40 mg/kg for two days as a single daily dose. Diabetes+Melatonin group was consist of the animals that treated with 50 mg/kg melatonin by intraperitoneally to streptozotocin induced diabetic during 8 weeks. In diabetic rats, the platelet count and fibrinogen level significantly increased compared to control group (p<0.05), whereas melatonin application to the diabetic rats caused to decrease in fibrinogen level when compared to diabetic rats (p<0.05). Activated Partial Tromboplastin Time (APTT), Prothrombin Time (PT) and International Normalized Ratio (INR) levels significantly shortened in the experimentally diabetes group compared to the control group (p<0.05). PT and INR significantly prolonged in diabetic rats with the melatonin treatment compared to diabetic rats (p<0.05). In conclusion, the obtained data indicated that administration of melatonin partly ameliorated procoagulant state caused by diabetes in rats.