Diabetes mellitus significantly affects the male reproduction and sexual function. In the present study, we investigated the diabetes-induced dysfunction of seminal vesicles (SVs) in the diabetes-rat model and the role of antioxidants. Streptozotocin-induced diabetes after 4 weeks caused smaller size of the organs, hypercontractility, histological abnormalities, increased concentrations of malondialdehyde in the serum and tissue, overexpression of oxidative stress markers, and cleaved caspase-3 as identified by immunohistochemistry in the SVs. In addition, diabetes resulted in deceased levels of serum testosterone and no newborns after the mating studies. Antioxidants significantly normalized all the above parameters, except for the severely decreased serum testosterone levels and the negative outcome of the mating studies. The present study gives evidence for the important role of diabetes-induced oxidative stress in the function and structure of these androgen-dependent organs. Antioxidants may be a promising supplementary therapy for diabetic male patients to alleviate ejaculatory disorders but alone is not efficient treatment for the mitigation of infertility.