Saphenous vein graft aneurysms are a rare but potentially fatal complication following coronary artery bypass graft (CABG) surgery, with a wide variation in clinical presentations ranging from recurrent atypical chest pain to sudden cardiac death. Although uncommon, the diagnosis should be considered in all patients presenting with a hilar or mediastinal mass following CABG, as timely treatment may avert potentially fatal aneurysm rupture and death. We report a rare case of a giant vein graft pseudoaneurysm rupture causing cardiac tamponade.