We present here a case of diffuse tracheobronchial wall spread of metastatic breast cancer who was successfully treated with trastuzumab plus vinorelbine chemotherapy. The patient had a left radical mastectomy for breast cancer in March 2000 and developed persistent cough and dyspnea in November 2006. Pulmonary function test demonstrated an obstructive pattern. Chest computed tomography showed a wall thickening of trachea and right side bronchus, but radiographic findings including (18)F-fluorodeoxyglucose positron emission tomography failed to detect the locations of disease in the lung. The findings on bronchofiberscopy showed edematous tracheobronchial mucosa, but also failed to visually detect direct masses. Transbronchial biopsy specimens revealed involvement of metastatic breast cancer. The patient was treated with trastuzumab plus vinorelbine chemotherapy and the wall thickening of bronchial tree and clinical symptoms were improved. Although endobronchial metastasis in metastatic breast cancer is not uncommon, diffuse spread without forming intraluminal mass is extremely rare. The pattern of endobronchial metastasis should be considered in patients with malignancies even when radiographic abnormalities are undetectable.