Carcinosarcoma of the lung is a rare turner with an admixture of malignant epithelial(carcinomatous) and malignant mesenchymal (sarcomatous) components. Clinicopathologically, pulmonary carcinosarcoma has been divided into two types by its anatomical locations and growth nature, peripheral parenchymal and central endobronchial variants. We experienced an endobronchial carcinosarcoma that induced complete atelectasis of the right lung due to polypoid growing mass from the right upper lobe bronchus in a 67 year old male smoker. The patient underwent a successful right pneumonectomy. The tumor was composed of squamous cell carcinoma with variable sarcomatous differentiation into myogenous and undifferenciated sarcoma that demonstrated by immunohistochemical study. The patient has been doing well for the last seven months since the operation, without metastases or turner recurrence.