The diagnosis of uterine smooth muscle tumors is usually not difficult. Occasionally, benign tumors with an unusual growth pattern may cause some diagnostic confusion for pathologists who had not experienced such a tumor before. A fifty-one year old female patient had admitted to our gynecology outpatient clinics with abnormal uterine bleeding (menorrhagia) and undergone a surgery with a diagnosis of pelvic mass. A neoplasm consisting of spindle cell nodules with prominent hydropic degeneration was observed at pathological examination. Tumor cells were positive for vimentin, desmin and smooth muscle actin at immunohistochemical evaluation. Cotyledonoid leiomyomas are rare benign smooth muscle tumors of uterus which are recently defined in the literature. In this article we report a case of cotyledonoid leiomyoma of uterus with an exophytic growth pattern in the serosa and did not contain an intramural dissecting component.