Infectious endocarditis (IE) concomitant with patent ductus arteriosus (PDA) is now considered rare because the early treatment of PDA in infancy has become standard. We report a case of PDA with IE diagnosed by computed tomography (CT). A 51-year-old man complained of arthralgia and numbness of the left extremities. He had fever of 39°C and left hemiplegia, and was referred to our hospital. A chest X-ray film showed infiltration in both lungs. CT revealed a mass lesion in the main pulmonary artery and a tubular connection between the main pulmonary artery and the aortic arch. Multiple small infarctions were also found in the brain, lungs, kidneys and spleen. Ultrasonic cardiography revealed a bi-leaflet aortic valve, and vegetations on the aortic and mitral valves. Staphylococcus aureus was detected by culture of an intravenous catheter tip. These findings suggested IE concomitant with PDA, and we started intravenous administration of antibiotics. However, congestive heart failure occurred due to severe aortic and mitral regurgitation 2 days after hospital admission, and therefore, we performed emergency surgery. The main pulmonary artery was incised after cardiopulmonary bypass was initiated. A 20-mm length of vegetation was found on the orifice of the PDA. The vegetation was removed and the PDA directly closed. Aortic and mitral valve replacement was then performed. The post-operative course was uneventful and his neurological symptoms did not exacerbate. No sign of IE recurrence was observed 2 years after the surgery. CT clearly showed PDA and vegetation in the main pulmonary artery, although ultrasonic cardiography did not. CT was useful to make a diagnosis of PDA with IE in the present case.