The patient, a 28-year-old woman, in her ninth week of pregnancy, was operated on for stage Ia, mixed germ cell tumor (grade 3 immature teratoma + yolk sac tumor) of AFP decreased to the normal level. Eight months later, an intrapelvic mass and raised AFP were found. The extirpated recurrent tumor in the pouch of Douglas was a grade 2 immature teratoma with no yolk sac element. FAM chemotherapy was given again, and the patient is alive and well after taking oral UFT. As in testicular germ cell tumors, ovarian germ cell tumors can be converted to a more differentiated tumor following chemotherapy.