Primary pulmonary synovial sarcoma is an extremely rare tumor. The diagnosis is established only after sarcoma like primary lung malignancies and metastatic sarcoma have been excluded. It has four subtypes: monophasic fibrous, monophasic epithelial, biphasic, and poorly differentiated subtypes, We report a case of a 55-year-old man, who complained of left-sided chest pain and shortness of breath, had a large heterogeneous mass, occupying most of left hemithorax, associated with ipsilateral pleural effusion, seen on contrast enhanced computed tomogram of thorax. Computed tomography guided tru-cut biopsy revealed spindle cell sarcoma. On immunohistochemistry, tumor cells expressed epithelial membrane antigen, CD99, bcl-2 and Calponin and were immunonegative for cytokeratin. So, final diagnosis was primary pulmonary synovial sarcoma, Primary pulmonary synovial sarcoma is a rarely reported case of malignant neoplasm of lung. Histopathology, immunohistochemistry, and cytogenetics, if possible, are essential for confirmation of its diagnosis.