Grade 3 immature teratoma of the ovary is rare and has a poor prognosis due to early recurrence. This report describes a case of grade 3 immature teratoma of the ovary that recurred 16 years after the last treatment. The patient underwent abdominal simple total hysterectomy, bilateral salpingo-oophorectomy, pelvic-para-aortic lymphadenectomy, and adjuvant chemotherapy under the diagnosis of grade 3 immature teratoma of the ovary when she was 15 years old, and complete remission was achieved. Sixteen years after the initial treatment, the tumor relapsed in her liver and pleura. She was treated by 10 courses of tri-weekly paclitaxel and carboplatin, and was alive with stable disease for 12 months after the disease relapse. After 1 year, the tumor progressed, and she died 16 months after the relapse. This is the first report of grade 3 immature teratoma of the ovary that relapsed more than 5 years after the prior treatment.