A 40-year-old man was admitted to our hospital with a 1-month history of dyspnea and appetite loss. Chest computed tomography and echocardiography showed moderate pericardial effusion and pericardial thickening. The patient had no history of exposure to asbestos. We created a pericardial window in order to make a diagnosis and to relieve the symptoms using video-assisted thoracoscopic surgery and performed biopsies of the pericardium and the pleura. Immunohistologic analysis of the pericardium confirmed a diagnosis of biphasic pericardial mesothelioma. We gave the patient two cycles of chemotherapy, including pemetrexed and platinum, but his condition did not improve and he died 3 months after onset.