"nMycotic pseudoaneurysm of the ascending aorta is rare in patients undergoing coronary artery bypass graft (CABG) and usually caused by staphylococcus aureus. We describe a patient with a mycotic pseudoaneurysm of the ascending aorta at the proximal vein graft anastomosis site after CABG. Culture from the sinus tract of the sternum and from the aneurysm sac was Klebsiella pneumoniae. Surgical technique was patch repair of aorta under hypothermic circulatory arrest. He is asymptomatic at 24 months follow-up