A major diagnostic challenge to the evaluation of an incomplete intestinal obstruction is to distinguish between infectious and malignant etiologies. We present a case of an elderly woman complaining of abdominal pain accompanied with nausea and vomiting, and failure to pass gas or stools. Anti-tuberculosis drugs were used to relieve her abdominal pain, and a needle biopsy of the peritoneal cavity showed evidence of primary papillary serous carcinoma of the peritoneum (PSCP). This is a rare description of tuberculosis in the setting of PSCP. This report illustrates the potential complex nature of malignancies, and emphasizes the need to consider coexistence of malignancy and infection in patients, especially in those with risk factors for malignancy who fail with antibiotic therapy.