Pseudoaneurysm of the ascending aorta after cardiac surgery is a rare but life threatening complication, which can result in rupture. Pseudoaneurysms are usually related to the aortic cannulation, the proximal site of graft anastomosis, or the suture line of aortotomy, and often occur after mediastinal infection. We report a case of pseudoaneurysm of the ascending aorta associated with aortic cannulation and the proximal anastomosis of a saphenous vein graft without an obvious history of mediastinal infection.