Alpha-fetoprotein producing tumors other than hepatoma and germ cell tumors have been widely reported, especially in carcinoma with hepatoid differentiation (hepatoid carcinoma). Hepatoid carcinoma has mostly been found in the stomach, but also occurs in many other organs. A rare case of hepatoid carcinoma of the ovary is presented. A 57-year-old Taiwanese woman was admitted because of lower abdominal pain. Magnetic resonance imaging showed a 10 cm right adnexal mass. She underwent a total hysterectomy and bilateral salpingo-oophorectomy with omentectomy. A right ovarian mass measuring 13 x 9 x 8 cm was found. Microscopic examination showed characteristic features for hepatoid carcinoma. Immunohistochemical staining was performed on the tumor using a panel of eight markers (AFP, p-CEA, CD10, Hep Par 1, thyroid transcription factor-1, CK7, CK19 and CK20). This study contradicts the theory that hepatoid carcinoma derives from the surface epithelium of the ovary. Hepatoid carcinoma of the ovary commonly contains a population of clear cells, which may lead to the misdiagnosis of yolk sac tumor or clear cell adenocarcinoma that may arise in many anatomic sites. Histologically, it is also difficult to distinguish hepatoid carcinoma from hepatoid yolk sac tumor. In such cases, demonstration of CD 10, Hep Par 1, membraneous patterns of p-CEA and CK7 would be invaluable for characterizing the tumor as hepatoid carcinoma. More studies are needed to confirm this observation.