Synovial sarcoma is a malignant soft tissue neoplasm that occurs frequently in the extremities of young adults, near large joints. The lung is a common site of metastasis but an extremely unusual primary site for synovial sarcoma. We report an unusual case of primary synovial sarcoma that arose in the lung of a 59-year-old woman. The tumor had histologic and immunophenotypic features consistent with biphasic synovial sarcoma. These features included of an intimate admixture of cytokeratin and epithelial membrane antigen(EMA)-positive neoplastic epithelial cells and vimentin-positive fibroblast-like spindle cells. The patient had a closed thoracomy drainage and doxycycline pleurodesis for malignant loculated effusion and showed tumor extension in the left whole lung 4 months after pleurodesis. This case is an usual addition to the small number of published reports on primary pulmonary synovial sarcoma. The distinctive features of this neoplasm allow it to be distinguished from a variety of primary and metastatic malignancies in the lung.