Background. Intraabdominal lesions such as mesenteric cysts are uncommon disorders. Most are discovered incidentally during routine abdominal examinations. Methods. We report a patient with a mesenteric cyst masquerading as tuberculous peritonitis and ascites. Conclusion. Mesenteric cysts generally do not show typical clinical findings. They may also present with peritoneal tuberculosis findings such as low albumin gradient ascites with high ascitic adenosine deaminase levels. Surgery is used to remove a wide variety of mesenteric cysts. A correct diagnosis can be made by the combined use of radiographic and sonographic examinations in conjunction with the clinical signs. Copyright © 2010 Cumhur Dulger et al.