Diagnosis of malignant germ cell tumors of the ovary is usually difficult because many ovarian neoplasms have similar clinical and radiologic manifestations. We reviewed retrospectively 12 cases of ovarian malignant germ cell tumor and evaluated with respect to size, mass characteristics on computed tomography for differential diagnosis. Endodermal sinus tumors were mainly cystic mass with some solid component and septations. Immature teratomas showed typical manifestations, such as fatty tissue, calcifications, cysts, and irregular shaped soft tissue densities. Dysgerminoma was mainly solid mass without cystic component, and mixed germ cell tumor showed nonspecific manifestations. All cases were relatively large in size, and young in age. In conclusion, CT findings of malignant germ cell tumors are helpful in differential disgnosis.