This work aimed to investigate the role of diabetes on cell proliferation, and apoptosis in testis. The rats were randomly allotted into one of two experimental groups: control and diabetic group; each group contain 10 animals. Diabetes was induced by a single intraperitoneal injection of STZ (50 mg/kg). Testicular damage was examined by using hematoxylin and eosin, immunohistochemical staining of proliferating cell nuclear antigen (PCNA), and apoptosis was determined by terminal-deoxynucleotidyl-transferase mediated dUTP nick end labeling (TUNEL). Potential disorders associated with seminiferous tubular sperm formation were evaluated using the Johnsen score. The mean seminiferous tubule diameter (MSTD) and mean testicular biopsy score (MTBS) values were significantly decreased in diabetic group was compared to the control group. Our data indicate a significant reduction in the expression of PCNA and an enhancement in the activity of TUNEL in testis tissues of the diabetic group. The effects of diabetes on spermatogenesis can be clearly detected as a testicular cell death and decrease in MTBS, MSTD, and PCNA expression.