Preoperative delayed-enhanced magnetic resonance imaging (DE-MRI) was performed to estimate myocardial viability in a 57-year-old man with ischemic cardiomyopathy in order to decide the best course of treatment. The patient was diagnosed as having congestive heart failure with triple-vessel involvement (ejection fraction of 7%, end-diastolic volume index of 160 ml/m2, end-systolic volume index of 148 ml/m2). 99mTc-sestamibi single-photon emission computed tomography revealed severe reduction of the uptake at both stress and resting phases in the anterior, lateral and inferior segments. However, DE-MRI demonstrated transmural hyperenhancement to be <25% within the whole ventricular wall, implying that, though there was extensive subendoventricular myocardial infarction, there was substantial viable myocardium. Therefore, with the expectation that functional recovery was possible with coronary revascularization alone, we performed a complete revascularization with off-pump coronary artery bypass grafting. Six months after the operation, catheterization demonstrated dramatic improvement in ventricular function, with the ejection fraction having increased to 36%. This case suggests that preoperative assessment of myocardial viability by DE-MRI could help cardiac surgeons to choose the best treatment for patients with ischemic cardiomyopathy.