We report the clinical, sonographic, and pathologic findings of an incidentally discovered testicular granulosa cell tumor of the adult type in a 32-year-old man. Serum tumor markers were within normal limits. The sonographic findings revealed a well-circumscribed, hypoechoic mass. Gross inspection confirmed a unilobular, well-circumscribed mass without necrosis. Microscopically, the mass was demarcated by a thin capsule, with tumor cells arranged in nests with low mitotic activity. These cells were diffusely immunoreactive for vimentin and focally for inhibin. The entrapped rete epithelium stained positive for pancytokeratin (Lu-5). We present our management of this rare malignancy.