Background. Thoracoscopy is a useful technique for the causative diagnosis of exudative pleural effusions with unknown etiology on routine pleural fluid examinations. Malignant lymphoma should be considered as a potential cause of exudative pleural effusion. Case. A 71-year-old man was referred to our institute because of left exudative pleural effusion on an annual routine health checkup. Repeated thoracenteses showed lymphocyte-dominant exudative pleural fluid but could not identify the cause of the pleural fluid despite detailed examinations, including adenosine deaminase and cytological examinations of the pleural fluid. At that time, the patient did not wish to undergo a further invasive examination and was therefore followed up at the outpatient clinic. Approximately one year after the first visit, the pleural effusion had increased, and chest computed tomography and fluorodeoxyglucose-positron emission tomography revealed progressive tumorous lesions on the parietal pleura at the post-sternal space and around the anterior wall of the heart. A thoracoscopic examination revealed a light-brown, smooth and relatively soft surface tumor lesion from the post-sternal space to the anterior surface of the heart. The diagnosis of mucosa-associated lymphoid tissue (MALT) lymphoma was made upon a detailed histological examination of the pathological specimen of this lesion. Conclusion. We herein report a rare case of MALT lymphoma, which developed in the parietal pleura, in the post-sternal space and on the anterior surface of the pericardium, presenting as recurrent pleural effusion. A thoracoscopic biopsy was useful for the diagnosis in this case.