Most thoracic aortic aneurysms are asymptomatic and are detected by chance on routine chest imaging for some other reasons. Only rarely it is symptomatic due to leak and dissection which is a potentially life threatening event that commonly presents with severe pain. In this report, we present the case of a 67-year-old man who presented with shortness of breath, intermittent cough, fever, and left sided painless hemorrhagic pleural effusion. Further investigation by plain radiography, computed tomography and magnetic resonance imaging revealed a saccular aneurysm arising from the lateral aspect of the mid-transverse arch of the aorta, along with a dissecting descending aortic aneurysm with false lumen communicating with left pleural space. The patient refused any surgical procedure and was treated conservatively with blood transfusions and anti hypertensive medication. On the 8th day patient finally succumb to a fatal episode of shock. We suggest dissecting thoracic aneurysm be included in the differential diagnosis of non-traumatic hemorrhagic pleural effusion in an elderly patient presenting with dysnea, cough and fever, which otherwise suggest the clinical diagnosis of bronchogenic carcinoma. Computed tomography of the chest should be immediately performed as the diagnostic procedure of choice.