On the basis of computed tomography (CT) examination, a prosthetic graft infection of very late onset was suspected in a 72-year-old man who had undergone replacement of an bifurcated prosthetic graft 6 years earlier because of an abdominal aortic aneurysm and bilateral common iliac artery aneurysms.Emergency CT-guided needle aspiration was performed, and analysis of directly aspirated fluid confirmed the rapid diagnosis. Instead of conventional emergency surgery, CT-guided catheter drainage was the initial treatment and led to the gradual improvement of symptoms and laboratory data. Elective staged surgery was performed later to examine the cavity around the prosthetic graft. The cavity was then filled with in-situ omentum. Thus, CT-guided catheter drainage as the initial treatment and following omentopexy as the staged surgery avoided the need for highly invasive conventional surgery. (J Nippon Med Sch 2016; 83: 203 205)