Poly (ADP-ribose) polymerase inhibitors exhibit strong activity for treating the DNA damage repair defect in patients with prostate carcinoma (PCa). Although conventional DNA-damaging agents can theoretically lead to synthetic antitumoral effects, no report has clearly mentioned the clinical use of cisplatin for treating PCa patients with the breast cancer gene (BRCA)2 mutation. We administered 80 mg/m2 cisplatin triweekly to a patient with metastatic castration-resistant PCa (mCRPC) with the BRCA2 mutation, and after ten cycles, the prostate-specific antigen was dramatically decreased. We suggest that BRCA2 mutations may indicate the use of cisplatin for treating patients with mCRPC.