Ovarian primary malignant melanoma is very uncommon with only 44 reported cases in the literature. A 71-year-old woman with an ovarian mass and multiple nodules in the liver presented to our hospital. She was treated with bilateral salpingo-oophorectomy, and malignant melanoma was found in the mature cystic teratoma of the ovary. Malignant melanoma cells were also found in the ascitic fluid. She died 5 months later. Here we report a very uncommon case of malignant melanoma arising in an ovarian mature cystic teratoma with a review of the literature.