We report a case of small cell lung cancer with an initial symptom of breast metastasis. A 55-year-old woman was admitted complaining of multiple breast masses. Chest computed tomography (CT) and magnetic resonance imaging (MRI) showed a left hilar mass. Specimens obtained from a breast mass and transbronchial biopsy revealed neoplastic cells suggesting small cell carcinoma Small cell lung cancer with breast metastasis was diagnosed. Systemic chemotherapy resulted in partial remission of the primary lesion and breast metastases.