ABSTRACT Pulmonary adenocarcinoma is a malignant epithelial neoplasia that usually arises from conducting airways or alveolar parenchyma. It has rarely been described in wild felids, with no previous reports in ocelots. In domestic cats it is a very aggressive neoplasm with a high metastatic rate that usually evolves to death. This report aimed to describe a pulmonary adenocarcinoma in a captive and senile ocelot (Leopardus pardalis), with a thorough morphologic and immunophenotypically characterization, evidencing the epithelial-mesenchymal transition (EMT) phenomenon in a high metastatic carcinoma, an important feature rarely described in veterinary medicine, even in domestic cats.