Most common ovarian germ cell tumors are mature cystic teratomas (MCTs), comprising 10 to 25 percent of all ovarian neoplasms. MCTs are usually benign in nature but have the potential of undergoing malignant transformation, typically in postmenopausal women, with an incidence of 0.17 to 3 percent. The most common malignant tumor arising in MCT is a squamous cell carcinoma. We present an unusual clinical entity in a 56 year old woman of a squamous cell carcinoma arising within a mature cystic teratoma.