A 46-year-old woman presented with whole abdominal discomfort, and imaging revealed a 3-cm-sized ill-defined ovarian mass with extensive peritoneal carcinomatosis. Histologic examination showed malignant fibrous histiocytoma of ovary with predominant myxoid stroma. Microscopic examination showed a highly cellular neoplasm composed of fibroblast-like cells with a predominant myxoid stroma and high pleomorphism and mitotic activity. Immunohistochemically, the tumor was negative for smooth muscle actin, desmin, S-100, pancytokeratin, c-kit, epithelial membrane antigen, and calretinin. Malignant fibrous histiocytoma of ovary is extremely rare, with only six previously reported cases. To the best of our knowledge, the myxoid type of malignant fibrous histiocytoma of ovary has not been previously reported in the English literature except for a case arising in a dermoid cyst of ovary. We present the case and briefly discuss the differential diagnosis.