Background & Objective: Cardiovascular diseases (CVDs) are the deadliest disease globally, which in order to reduce this mortality rate statin has been used during last decades. In line, it has been revealed that statins negatively affect testicular tissue. Thus, in the current project, we aimed to investigate the vitamin D protective effects during simvastatin (SIM) administration.
 Materials & Methods: In this project, 48 male mature Wistar rats were randomly divided into 6 control and experimental groups. The experimental groups were subdivided into Low and High dose SIM-received and Vitamin D co-treated SIM-received groups. After 45 days, the body weight of the animal groups was measured and then they were euthanized and testicles were removed. The right testicular tissue was fixed in fixative solution, while the left testicular tissue was used for biochemical and molecular analysis. To evaluate the pathological changes, hematoxylin and Eosin (H&E) staining were performed. The Malondialdehyde (MDA), Total antioxidant capacity (TAC), catalase (CAT) and Ferric-reducing antioxidant power (FRAP) levels were examined in order to evaluate the Reactive oxygen species (ROS) and antioxidant levels. Finally, Bax, Bcl-2, p53 and Caspase-3 mRNA levels were analyzed using real- time PCR.
 Result: Our observations revealed that the MDA, Bax, p53 and caspase-3 level enhanced in the sole-SIM-received groups compared to control group, while level of TAC, catalase and Bcl-2 diminished in SIM-received groups versus control group. In contrast, Vitamin D-co-treated animals showed a significant enhancement in level of TAC, catalase and Bcl-2 compared to sole-SIM-received animals (p≤0.05).
 Conclusion: The vitamin D-co-administration can positively protect testicular tissue against SIM-induced oxidative stress condition by enhancing enzymatic activity of antioxidant defense and anti-apoptotic genes activation.