We report a case of uretero-appendiceal fistula. A 63-year-old woman was admitted to our hospital with high grade fever and loss of 5 kg of body weight over 6 months. Pyonephrosis was diagnosed. A retrograde ureterogram and barium enema showed a connection between cecum and ureter. Right nephroureterectomy and right hemicolectomy were carried out. The final diagnosis was uretero-appendiceal fistula.