Spontaneous hemothorax is less common. We report the case of an 83-year-old woman with spontaneous hemothorax caused by lung cancer with nontuberculous mycobacteriosis. She presented with chest pain and hemoptysis. Computed tomography revealed a tumor in the right middle lobe with middle syndrome and pleural effusion. Hemothorax was confirmed, and the right middle lobe was resected to control bleeding. The lung tumor invaded the mediastinal tissue, and tumor rupture was observed. Histological examination revealed pulmonary spindle cell carcinoma and epithelioid granulomas with caseous necrosis. Rapid tumor growth and mediastinal invasion could have led to intratumoral hemorrhage and tumor rupture.