A 10-year-old miniature sow was died, showing inappetence and weight loss. Grossly, neoplastic enlargement of the uterus was found. Histopathologically, the lesions consisted of acinar, ductular and cystic proliferations of mono- and multilayered epithelial cells; these cells reacted immunohistochemically strongly with three different cytokeratin antibodies, and occasionally to vimentin. Myofibroblastic desmoplastic cells, positive to alpha-smooth muscle actin, were present among neoplastic cells. Metastatic lesions were seen in the lungs and liver. Based on these findings, a diagnosis of uterine adenocarcinoma with marked desmoplasia was made. This case is the second report of uterine adenocarcinoma in the miniature pig.