Primary peritoneal serous papillary carcinoma (PSPC) is a rare primary peritoneal tumor. Clinically, PSPC usually presents with general abdominal discomfort resulting from variable amounts of ascites. In a state of small amounts of ascites, initial manifestation of massive bilateral pleural effusion is unusual. A 76-year-old female nonsmoker with no asbestos exposure complained of dyspnea during exercise. Chest radiograph showed a massive bilateral pleural effusion. Chest computed tomography (CT) revealed irregular pleural thickening and a small amount of ascites. Abdominopelvic CT revealed nodular thickening of the parietal peritoneum, mesenteric or omental nodules, omental cake, and lymphadenopathy in paraaortic regions. Adenocarcinoma cells were found via cytologic examination in bilateral pleural fluids and ascites. Because the primary site of the adenocarcinoma was not found, a surgical biopsy of the right pleural thickening was performed. The final diagnosis was PSPC. The patient was treated with platinum-based chemotherapy. Physicians should be aware of a possibility of PSPC when the radiographic findings show massive bilateral pleural effusion due to pleural carcinomatosis, with high serum levels of CA125.