We herein present a 60-year-old man with adrenocortical carcinoma who had gynecomastia. An endocrinological examination revealed increased levels of serum estradiol and dehydroepiandrosterone-sulfate (DHEA-S) and reduced levels of free testosterone. Magnetic resonance imaging showed an adrenal tumor with heterogeneous intensity. Iodine-131 adosterol scintigraphy showed an increased uptake at the same site. Because feminizing adrenocortical carcinoma was suspected, right adrenalectomy was performed; the pathological diagnosis was adrenocortical carcinoma. The results of immunostaining indicated a virilizing tumor. Aromatase activity was identified on RT-PCR. As disorganized steroidogenesis is pathologically present in adrenocortical carcinoma, this diagnosis should be made with caution.