A 7-yr-old, intact, female swift fox (Vulpes velox) presented to the Veterinary Health Center at Kansas State University with a history of chronic weight loss, lethargy, inappetence, and myiasis. On physical examination, a firm mass was palpated in the mid- to cranial abdomen. The fox was euthanatized as a result of the grave prognosis. Gross necropsy and histologic findings included a small intestinal adenocarcinoma with diffuse transperitoneal spread throughout the abdominal cavity (carcinomatosis). To the authors' knowledge, this is the first report of intestinal adenocarcinoma with carcinomatosis in a swift fox.