A uterine adenocarcinoma with widespread visceral implantation and lymphatic metastases is described in a 4-yr-old captive nulliparous sika deer (Cervus nippon). The tumor was histologically characterized by proliferation of irregularly shaped acini and tubules lined by single- or multi-layered pleomorphic epithelial cells, which were sometimes multi-nucleated and contained PAS positive mucin. The neoplastic tissue was invasive and showed a marked desmoplastic reaction. A relationship between the tumor and a hormonal imbalance could not be ruled out. This is the first report of a tumor of the reproductive tract in a cervid.