Primary ovarian leiomyosarcomas are extremely rare tumors that comprise less than 0.1% of all ovarian malignancies. We present a case of 62-year-old postmenopausal woman with a slightly enlarged right ovary and a Color Doppler sonography resistance index (RI) measuring 0.54. The patient, after being managed with surgery alone, is alive after 14 months without any evidence of disease. This is an unusual case in that primary ovarian leiomyosarcoma was diagnosed in the setting of a slightly enlarged irregular postmenopausal ovary with a concomitant intermediate RI value on color flow Doppler evaluation. A high index of suspicion may help prevent delay in the diagnosis of this rare neoplasm.