An embryonal carcinoma was diagnosed in the abdominal cavity of a 55-day-old male calf. Macroscopically, a large volume of ascitic fluid was observed along with white to yellowish-white masses of various sizes densely located on the abdominal wall and the surface of abdominal organs. There was an absence of testes in the scrotum. Histologically, the tumor cells were polygonal, and the tumor was mostly composed of sheets of densely packed solid patterns with occasional papillary and tubular structures. Cell nuclei were variable in size, and cellular mitotic rate was high. Immunohistochemically, tumor cells were positive for alpha-fetoprotein, placental alkaline phosphatase, cytokeratin, and carcinoembryonic antigen. Ultrastructurally, the tumor cells had large nuclei, extensive rough endoplasmic reticulum, and small numbers of mitochondria. Microvillus-like structures and desmosomes were occasionally observed. From lectin histochemical examination, the tumor cells were positive for concanavalin A, wheat germ agglutinin, peanut agglutinin, Dolichos biflorus agglutinin, soybean agglutinin, Griffonia simplicifolia I, and Bauhinia purpurea, and negative for Ulex europaeus agglutinin I. Results of histopathological, immunohistochemical, and ultrastructural examinations of the tumor were similar to those obtained for human embryonal carcinoma.