Mature cystic teratomas of the ovary are one of the most common ovarian neoplasms found in reproductive age women. Malignant transformation is an uncommon complication in a mature cystic teratoma of the ovary, usually being reported in about 1-3% of cases. Of malignant transformations, squamous cell carcimona is the most common type and sarcomatous transformation is rare, its prognosis is poor. Adenocarcinoma occurs with less frequency. We experienced a case of squamous cell carcinoma and adenocarcinoma arising in mature cystic teratoma of the ovary, so we present this case with brief review of the literature.