Tuberculous peritonitis is a rare cause of intra-abdominal infection. Although sometimes asymptomatic, most of the patients have fever, weight loss, abdominal pain, and edema. The diagnosis of tuberculous peritonitis is difficult and sometimes delayed because of confusion of the disease with other illnesses and the non-specificity of signs and symptoms. Tuberculous peritonitis is examined with ultrasonography and computerized tomogram, but confirmed by biopsy or tuberculosis culture. Ascitic fluid is exudates with a lot of lymphocytes and elevated protein. Tuberculous peritonitis is treated successfully with isoniazid, rifampicin for one year, pyrazinamide for first 2 months and streptomycin for first one month. We experienced one case of tuberculous peritonitis with transudate of ascitic fluid, confirmed by biopsy using colonoscopy, and treated successfully.