Cotyledonoid leiomyoma or "grapelike" leiomyoma is a very rare tumor among the ever-expanding repertoire of growth variants described in benign uterine leiomyoma. We report a case of cotyledonoid leiomyoma in a 55-year-old woman who presented with menorrhagia and uterine prolapse. A large multinodular fungating tumor adhering to the right posterolateral wall of the uterus and extending to the broad ligament was discovered at vaginal hysterectomy. With a provisional diagnosis of sarcoma, total hysterectomy and bilateral salpingo-oophorectomy were performed. Postoperatively, the patient was well with no evidence of recurrence at 14 months. Pathologic examination revealed a 10-cm, red-brown tumor that comprised multiple bulbous processes protruding over the uterine surface, in continuity with a dissecting intramyometrial component. It was composed of fascicles and nodules of bland-looking smooth muscle cells with prominent perinodular hydropic degeneration. Coagulative necrosis, mitoses, and nuclear atypia were absent. Cotyledonoid leiomyoma apparently results from a combination of several uncommon growth patterns operating together, including subserosal growth, dissecting growth, and perinodular hydropic degeneration. Increased awareness of this grossly alarming variant of benign uterine leiomyoma can help avoid overtreatment.