Apart from typical yolk sac tumors, ovarian tumors with elevated alfa-fetoprotein (AFP) are uncommon and the differential diagnosis needs to consider the hepatoid pattern of a yolk sac tumor, hepatocellular carcinoma metastatic to the ovary, hepatoid carcinoma, and other epithelial ovarian tumors. We report here an AFP-producing ovarian tumor with uncertain pathological diagnosis, which was extremely responsive to chemotherapy. A 59-year-old Japanese woman presented with lower abdominal distension and was found to have a left ovarian mass on pelvic examination and magnetic resonance imaging (MRI) scan. Laboratory tests showed serum AFP, 73 687 ng/ml; carbohydrate antigen 125 (CA125), 1599 U/ml; and carcinoembryonic antigen (CEA), 13.9 ng/ml. Total hysterectomy with bilateral salpingo-oophorectomy, partial omentectomy, and low anterior resection of the rectum was performed, without any residual macroscopic tumor. Microscopically, the tumor was characterized by a hepatoid carcinomatous component composed of solid sheets of large eosinophilic cells with pleomorphic nuclei. The pathological stage was pT2N0M0. Tumor cells were diffusely immunoreactive for AFP and cytokeratin (CAM5.2), but monoclonal CEA and CA19-9 were focally positive in the cytoplasm, while CA125 was negative. The patient was treated postoperatively with three cycles of chemotherapy consisting of bleomycin, etoposide, and cisplatin; with this regimen, serum AFP decreased to 16 ng/ml from 12 600 ng/ml just before the initiation of chemotherapy. The patient received secondary cytoreductive surgery of systemic lymphadenectomy, which revealed no evidence of residual tumor.