Tuberculous peritonitis is one of the most common causes of exudative ascites, especially in the young, and is an important cause of extra-pulmonary disease. However, tuberculous peritonitis is challenging to diagnose because there are no pathognomonic clinical features or imaging findings. Therefore, it is commonly misdiagnosed as another type of peritoneal disease, especially so in elderly patients with malignant disease. In this report, we described two cases of tuberculous peritonitis that were observed after intestinal perforation in elderly patients with malignancies. These diagnoses were established by laparoscopic peritoneal biopsy or AFB cultures of the ascitic fluid. Both patients were treated with anti-TB medications.