The most frequently occurring retroperitoneal tumors are those of the kidneys, adrenal glands, and the pancreas. A primary retroperitoneal tumor composed of granulosa cells and developing far away from the normal location of the ovary is less frequently observed. A 69-year-old female patient presented with abdominal discomfort. Computerized tomography (CT) of the abdomen revealed a solid heterogeneous mass lesion measuring 11.2 cm × 8 cm × 12 cm consistent with retroperitoneal hematoma. Ultrasonography (USG)-guided aspiration smears revealed cytological features suggestive of adult-type granulosa cell tumor (AGCT). As the patient had a history of hysterectomy with bilateral salpingo-oophorectomy 22 years ago for leiomyoma, a diagnosis of extraovarian AGCT was made. Intraoperatively, the tumor was removed in piecemeal that showed yellowish areas with extensive necrosis and hemorrhage. Histopathological examination of the excised mass and inhibin positivity confirmed the diagnosis. Primary retroperitoneal extraovarian GCT is a rare tumor with only 12 cases reported in medical literature in English.