Oxytocin (OXY) plays a crucial role in reproduction. The aim of this study is to investigate the therapeutic and protective effects of oxytocin treatment on streptozotocin (STZ) induced diabetes in testicular tissue. The rats were randomly divided into four experimental groups: (I) Control Group, (II) STZ induced Diabetic Group (STZ Group), (III) STZ induced Diabetic Group with Pre-Oxytocin treatment (Pre-OXY Group) and ( IV) STZ induced Diabetic Group with Post-Oxytocin treatment (Post-OXY Group); each group contains six animals. The rats whose blood glucose levels were more than 200 mg/dl were included to the experiment. At the end of the 4th week, testes tissue samples were taken to be processed for light microscopy and transmission electron microscopy. Malondialdehyde (MDA), Glutathione (GSH) and Advanced Oxidation Protein Products (AOPP) levels were determined biochemically in blood samples. Testicular tissue samples stained with Hematoxylin and Eosin (H&E) and Periodic acid-Schiff (PAS) reaction were evaluated under light microscope. The histopathological damage score of testicular tissue, which was significantly increased in STZ group, was decreased by oxytocin treatment. According to biochemical data, MDA and AOPP levels have been increased in the blood of STZ Group compared to the Control Group whereas they decreased significantly in Oxytocin-treated Groups compared to STZ Group. GSH levels were significantly decreased in the blood of STZ Group and increased in the blood of Oxytocin-treated Groups compared to STZ Group. In conclusion, oxytocin has a potential protective effect on the testes tissue of STZ-induced diabetic rats. (C) 2014 Elsevier Inc. All rights reserved.