Malignant transformation of a benign cystic teratoma of the ovary is only rarely seen. A review of the English literature revealed no reports of a malignant melanoma developing from concurrent primary endometrial carcinoma and ovarian cystic teratoma. We report herein a 54-year-old nulliparous woman who underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy for a pelvic mass and was diagnosed by histopathological examination to have a malignant melanoma developing from concurrent primary endometrial carcinoma and ovarian cystic teratoma. No foci of primary malignant melanoma except for the ovary were found upon clinical examination. The patient received postoperative interferon alpha 2B and radiotherapy. She was still asymptomatic at 12 months of follow-up.