A 56-year-old woman suffered from hepatic and bone metastases of breast cancer. Two months after starting combination chemotherapy with trastuzumab and docetaxel, air-space consolidation was observed in the right lower lung lobe on a chest computed tomography (CT) and a high serum KL-6 level was detected. Drug-induced pneumonitis with organizing pneumonia type was suspected, however, a transbronchial lung biopsy and cytological examination of the bronchoalveolar lavage fluid provided evidence of metastatic breast cancer. While the lung is a frequently affected site from metastasis of breast cancer, we report a rare case presenting as air-space consolidation on a chest CT.