Primary lung sarcoma is an extremely rare tumor accounting for less than 0.5% of all malignant lung tumors. Diagnosis is mostly established postoperatively. In this article, we present a 29-yearold male patient with a lobulated and well-marginated mass in the lower lobe of the right lung. A diagnosis of monophasic fibrous synovial sarcoma of the lung was established after right lower lobectomy. Resection margins were tumor-free. Postoperative positron-emission tomography/computed tomography did not show any other primary or metastatic focus. Despite the lack of a preoperative diagnosis, the advised treatment in such tumors is complete resection ensuring tumor-free surgical margins.