A 61-year-old man was admitted to our hospital with cough, bloody sputum, and chest pain. Bronchoscopy showed a tumor in the truncus intermedius which biopsy and brushing cytology revealed to be squamous cell carcinoma. Also, bronchial washings grew only N. asteroides. Treatment with minocycline and trimethoprimsulfamethoxazole (TMP/SMX) over one month resulted in some improvement in pulmonary symptoms and resolution of the infiltrates in the right lower field. Then, right pneumonectomy was performed. N. asteroides was isolated from the resected tumor. Aggressive bacteriological examinations should be utilized when the possibility of pulmonary nocardiosis is considered.