Objective: Extraovarian granulosa cell tumor is a very rare neoplasm. We report a case of a tumor located in mesocolon. Method: A 58-years-old woman presented with abdominal pain and fever. Abdomen CT showed a mesocolic mass adherent to the left kidney and the spleen. She underwent resection of a 22 cm long segment of the left colon with a circumscribed mesocolic tumor measuring 7×10 cm. The tumor was infiltrating the subserosa of the large intestine. Intraoperatively normal ovaries have been identified. Results: Histologically the tumor is composed by monomorphous cells in solid nests developing cavities which contain serous or hemmorhagic fluid. The tumor cells have scanty cytoplasm and often grooved nuclei. Mitoses are very rare. The tumor cells were immunoreactive for vimentin, inhibin and progesterone receptors. The postoperative course was uncomplicated and the patient is free of disease 18 months later. Conclusion: Light microscopic and immunohistochemical features of the tumor are similar to those of ovarian granulosa cell tumors (GCT). Since the tumor was resected in toto and the mitotic activity of the cells is very low, we expect a favorable prognosis. Extraovarian GCT are very rare and only 7 cases have been published during the last 50 years. Probably these tumors arise from residual tissue of the genital ridge (so-called secondary mullerian system).