The peritoneum is one of the common extrapulmonary sites of tuberculosis infection. Patients with underlying end-stage renal or liver disease are frequently complicated by tuberculous peritonitis; however, the diagnosis of the tuberculous peritonitis is difficult due to its insidious nature, well as its variability in presentation and limitation of available diagnostic tests. Once diagnosed, the preferred treatment is usually antituberculous therapy in uncomplicated cases. However, surgical treatment may also be required for complicated cases, such as small bowel obstruction or perforation. An 85-year-old woman was referred our hospital for abdominal pain with ileus. Despite medical therapy, prolonged ileus and progression to sepsis were shown, she underwent surgery to confirm the diagnosis and relief of mechanical ileus. Intraoperative peritoneal biopsy and macroscopic findings confirmed tuberculous peritonitis. Therefore, physicians should consider the possibility of tuberculous peritonitis in patients with unexplained small bowel obstruction.