Introduction: Cyclosporine A (CsA) is considered one of the potent drugs that are used extensively in organ transplant and oncology patients. It is also used in autoimmune diseases. Unfortunately, its use is accompanied with several hazards; one of these is testicular toxicity. Nacetylecysteine (NAC) is an antioxidant found to reduce CsA toxicity. Aim of the work: The study aims to determine the toxic effect of exposure to cyclosporine on the testis and to investigate the protective role of NAC. Methods: The study conducted on 50 adult male albino rats for 4 weeks divided into 5 groups, group A the negative control group, group B the olive oil group (0.5 ml/d orally), group C the cyclosporine group (25mg/kg/d orally), group D the NAC group (600mg/kg/d orally) and group E the cyclosporine+NAC group. At the end of the study the evaluation was achieved by biochemical analysis and histopathology. Results: Cyclosporine significantly affects the testis morphologically and functionally. The morphological changes are in the form of degenerative changes in the tubules with dislocation of germ cells into the lumen and irregular outlines, Congestion of blood capillaries in the interstitial tissue, and functionally the cyclosporine cause significant decrease in serum testosterone level. While co-administration of NAC with cyclosporine attenuate these effects. Conclusion: Cyclosporine causes testicular injury through oxidative stress and NAC as an antioxidant attenuates but not fully protect against cyclosporine induced testicular toxicity.