Hepatoid carcinoma (HCO) is a rare ovarian tumor and is thought to be a different subtype from hepatoid-type yolk sac tumor based on its pathologic features. In contrast to hepatoid yolk sac tumor in which the patients are usually young, patients with HCO are elderly with a peak incidence during the sixth decade of life. None of the patients with HCO have had gonadal dysgenesis or recognizable germ cell components within the tumors. We describe a case of a 42-year-old woman who presented to our hospital complaining of abdominal pain. Physical examination and CT scan revealed a large tumor in the left adnexa. She underwent total hysterectomy and bilateral salpingo-oophorectomy with omentectomy. A left ovarian mass measuring 11 cm in diameter was found. Histological diagnosis was hepatoid carcinoma of the left ovary. Immunohistochemical findings suggest that hepatoid carcinoma of the ovary is probably a most likely variant of a common epithelial carcinoma by a process of neometaplasia or transdifferentiation.