Congenital adrenal hyperplasia (CAH) can affect sex characteristics. The most common cause of CAH is 21-hydroxylase deficiency, and the cornerstone of treatment is glucocorticoid replacement in adrenocorticotropic hormone-suppressive dosages. A 64-year-old patient (46XX) with CAH resulting from 21-hydroxylase deficiency had been treated with dexamethasone and testosterone since diagnosis at age 12 and was phenotypically male. At age 62, he was diagnosed with prostate carcinoma. The patient received curative treatment with external beam radiotherapy. Genotypically female patients with CAH can develop prostate carcinoma when receiving long-term testosterone replacement therapy.