Mitotically active cellular fibroma (MACF) is characterized by increased cellularity, mitotic activity, and less frequently, nuclear atypia, which comprises 10% of ovarian fibromatous tumors. The authors report the case of a 76-year-old woman who presented at the present hospital with a two-month pelvic mass. B ultrasound disclosed a 75 × 52 × 41 mm mass in the right accessories. A hysterectomy and bilateral salpingo-oophorectomy was performed. Histologically, the tumor was composed of a densely cellular proliferation of fibrolastic-like cells with bland nuclear features and arranged in a fascicular pattern. There were more than four mitotic figures per ten high-power fields (HPFs). The histological diagnosis for the mass of the right ovary was MACF. MACF should be distinguished from ovarian fibrosarcoma. MACF is a recent histopathologic entity. Despite the high count of mitotic figures, the clinical course of the tumor is typically uneventful. Long-term clinical follow-up is recommended.