An 82-year-old man was diagnosed with lymphoplasmacytic lymphoma involving multiple lymph nodes and bone marrow. On radiological examinations no involvement of the lung was seen. He was treated with rituximab. Eighteen months later he was complicated with right pneumothorax, and surgery with bullectomy was finally performed. Histological examination disclosed the proliferation of abnormal B lymphocytes near the wall of the bulla and pleura. We conclude that the pneumothorax in this patient was associated with lymphoma. Thus, radiological examination does not disclose lymphomatous lesions, it is possible that lymphoma involves the pleura, and pleural involvement can cause pneumothorax. Surgery is an effective method of treating this rare complication.