Abstract. Primary ovarian leiomyosarcoma (POLMS) is a rare disease. To the best of our knowledge, only 72 cases, including the present case, have been reported in the English literature, while synchronous POLMS and fibroma in a single ovary have not previously been reported at all. In the present study, a 46-year-old premenopausal woman was diagnosed with a mass in the left ovary in 2005. A total of 5 years after the diagnosis of this mass, the patient was admitted to hospital exhibiting lower abdominal pain, and two masses were observed in the left ovary. An exploratory laparoscopy was performed. Frozen section analysis led to a diagnosis of fibroma. Furthermore, the observed second mass was hypothesized to be a malignant form of the original fibroma. A hysterectomy and bilateral salpingo-oophorectomy were performed. Pathological reports following surgery revealed concurrent stage Ic POLMS and fibroma in the left ovary. A total of 13 months after the initial surgery, recurrent leiomyosarcoma was detected. Although the patient underwent multiple cytoreductive surgeries and chemotherapy cycles, as well as interstitial brachytherapy and conventional therapy, a poor state of health ensued. Due to the rarity of POLMS, particularly in combination with ovarian fibroma, the current report presents a detailed overview of the literature and discusses a number of histogenetic and clinical issues.