This report details a case of prostatic carcinoma coexisting with a hemorrhagic cyst in a 66-year-old man; this combination was a challange for diagnosis and mamagement. The patient presented with lower urinary tract symptoms and a serum prostate-specific antigen (PSA) level of 33.3 ng/ml. Magnetic resonance imaging of the prostate showed a cystic mass with soft-tissue density and hemorrhage. Histological examination of the suprapubic prostatectomy specimens showed nodular hyperplasia with focal adenosis, high-grade prostatic intraepithelial neoplasia, a Gleason score of 6 for prostatic carcinoma, and a hemorrhagic cyst which appeared to be nonmalignant. We suggest that elevated serum PSA should raise the suspicion of coexisting malignancy in a hemorrhagic cyst.