Diabetes mellitus in human and animal models has been correlated with low sperm count, testicular abnormalities, high levels of germ cell death, and oxidative stress. In this study, we focus on three questions: (1) Is germ cell apoptosis stage-specific in diabetic male rats? (2) Could ascorbic acid (AA) reverse oxidative and histological damage and restore testicular dysfunction? (3) Could AA treatment restore fertility parameters in diabetic rats? Adult Sprague-Dawley rats were divided into four groups: control, diabetic, control plus AA, and diabetic plus AA. Seminiferous tubules underwent severe histological damage, together with a change in frequency of some stages of the seminiferous cycle, and germ cell apoptosis was increased in a stage-dependent manner in diabetic rats. We found a significant decrease in testosterone and higher levels of lipid peroxidation in diabetic rats when compared with controls. A major finding was that AA reversed the histological damage and peroxidation levels to control levels in diabetic rats, but testosterone levels remained unchanged. The pregnancy rate was decreased in females that mated with diabetic rats and those treated with AA, but the litter size was only reduced in the second case. Interestingly, spermatozoa from diabetic and AA-treated rats showed reduced motility and hyperactivation, but only diabetic rats had higher levels of apoptosis when compared with controls. These results suggest that treatment with AA reverses testicular damage in diabetic rats but is insufficient to restore testosterone levels, sperm motility, and fertility in a rat model.