Erectile dysfunction (ED) is associated with diabetes mellitus (DM). Pomegranate juice (PJ) is a potent antioxidant in diabetes induced oxidative stress. The aim of this study was to evaluate whether the administration of PJ ameliorates ED in streptozotocin (STZ)-diabetic rat model. Adult male Sprague-Dawley rats were divided into three groups (n=10-12, each): (1) Control, (2) STZ (25-35 mg kg-1, intravenously, 10 weeks) induced DM, and (3) PJ (100 mg kg-1 day-1, 10 weeks) treated DM rats. The in vivo erectile [a ratio of intracavernosal pressure (ICP)/mean arterial pressure (MAP)] and ex vivo corpus cavernosum (CC) responses were evaluated. Immunohistochemistry and Masson's trichrome staining were performed. Malondialdehyde (MDA) levels were measured. The ICP/MAP value in diabetic rats was lower than controls, which was partially improved by PJ treatment. Electrical field stimulation (EFS)-induced relaxant responses in CC from the diabetic group were significantly decreased that were ameliorated by treatment. Phenylephrine- and EFS-induced contractions were not altered in diabetic rats. PJ treatment normalized raised MDA levels of diabetic CC samples. Although the intensities of endothelial nitric oxide synthase (NOS) and neuronal NOS enzymes were decreased, inducible NOS protein levels were stronger in diabetic slides than controls. This is the first study to show that PJ treatment ameliorates partially ED and completely oxidative stress and fibrosis in a diabetic rat model. Our results highlight the success of antioxidant mechanism of PJ in ED with diabetes and open the way for future understanding in alternative treatment combinations with PDE5 inhibitors.