We report the case of a 36-year-old woman with congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency, and corticosteroid replacement therapy since birth. She manifested persistent virilization and high testosterone levels that were attributed to nonadherence to medical treatment. The patient was referred to our gender unit for genitoplastic surgery. We recommended the patient for left oophorectomy after detecting an ovarian mass. Pathologic findings confirmed an ovarian hilus cell tumor. Testosterone levels fell back to normal and masculinization disappeared but ACTH remained elevated. This case represents a very rare type of primary ovarian tumor that must be considered in persistent virilizing symptoms in women with CAH.