A 61-year-old man with a past history of pulmonary emphysema 6 years earlier was admitted to the emergency department at our hospital because of cough and dyspnea. Left pneumothorax was recognized on a chest radiograph. After his admission to the emergency department, chest drainage was inserted and the left lung was expanded. Afterwards, a nodular shadow (>1.5 cm) was found in the left upper lobe, and differentiation from pulmonary adenocarcinoma was required. As a definite diagnosis could not be made by bronchoscopy, video-assisted thoracoscopic surgery was performed, and a solitary nodule in the left upper lobe was resected. Histologically, a caseating epitheloid granuloma with acid-fast bacilli was found. Regarding the causative pathogen, Mycobacterium intracellulare was identified from the surgically resected specimen. We have reported a peculiar case of pulmonary M. intracellulare disease, detected at the onset of left secondary pneumothorax caused by pulmonary emphysema, which required differentiation from pulmonary adenocarcinoma.