Background: Prostate cancer is one of the most common solid tumors and the second leading cause of the death due to malignancy in men. Caspase 9 (CASP9) is a member of the intrinsic pathway and plays a central role in the apoptosis. Patients and Methods: Genotyping of the CASP9 (rs1052576) polymorphism were performed using real-time polymerase chain reaction for blood samples of prostate cancer patients (n=69) and controls (n=76). Results: There were no significant differences between the groups in the frequency of CASP9 genotypes (chi 2 = 1.363; p=0.506). Patients with CASP9 (rs1052576) CT genotype were 12.8 fold higher in pathological stage of pT2a compared to any other stages of cancer (OR=0.078, 95% CI= 0.009-0.062; p=0.004). Also TT genotype carriers were 11.3 times lower in pathological stage of pT2a (OR=11.33, 95% CI= 2.39-53.748; p=0.000). C allele carriers were 11.36 fold higher in pathological stage of pT2a compared to any other stages of cancer (OR=0.088, 95% CI= 0.019-0.418; p=0.002). Conclusion: CASP9 (rs1052576) C allele was decreasing the risk for pathological stage of patients with prostate cancer and also CT genotype had positive impact on pathological stage of patients with prostate cancer. CASP9 (rs1052576) TT genotype was seemed to be associated with higher risk of pathological stage. Those results implicated that CASP9 variations could be associated with severity of prostate cancer.