Subclavian artery stenosis or occlusion may be a cause of myocardial ischemia in patients treated using an internal mammary artery graft. Subclavian stenosis may cause myocardial ischemia during arm exercise by a coronary-subclavian steal phenomenon, with flow inversion in the graft from the coronary tree to the left subclavian artery. We here describe a case of a patient developing left subclavian occlusion after coronary artery bypass grafting with the left internal mammary artery. The lesion was successfully treated with a carotid-subclavian bypass. The article underscores the importance of an early diagnosis (possibly before bypass surgery) and discusses possible treatments. Percutaneous interventions with stent implantation appear the treatment of choice, but surgery has an important role in case of total occlusion.