Alterations of cardiac metabolism can be present in several cardiac syndromes. Heart failure may itself promote metabolic changes such as insulin resistance, in part through neurohumoral activation, and determining an increased utilization of non-carbohydrate substrates for energy production. In fact, fasting blood ketone bodies as well as fat oxidation have been shown to be increased in patients with heart failure. The result is depletion of myocardial ATP, phosphocreatine and creatine kinase with decreased efficiency of mechanical work. A direct approach to manipulate cardiac energy metabolism consists in modifying substrate utilization by the failing heart. To date, the most effective metabolic treatments include several pharmacological agents, such as trimetazidine and perhexiline, that directly inhibit fatty acid oxidation. These agents have been originally adopted to increase the ischemic threshold in patients with effort angina. However, the results of current research is supporting the concept that shifting the energy substrate preference away from fatty acid metabolism and toward glucose metabolism could be an effective adjunctive treatment in patients with heart failure, in terms of left ventricular function and glucose metabolism improvement. In fact, these agents have also been shown to improve overall glucose metabolism in diabetic patients with left ventricular dysfunction. In this paper, the recent literature on the beneficial therapeutic effects of modulation of cardiac metabolic substrates utilization in patients with heart failure is reviewed and discussed.