Metabolic syndrome represents a clustering of risk factors related to an elevated risk of cardiovascular disease and type 2 diabetes. Occurrence of both metabolic syndrome and diabetes and their vascular complications share several pathogenetic features including subclinical, low-grade inflammation, altered oxidative/antioxidant status, and persistent platelet activation. Despite the availability of multiple interventions to counteract these metabolic changes, including appropriate diet, regular exercise, weight control and drugs, epidemiological data are witnessing the growing trend of the problem, reflecting both the multifactorial nature of these diseases as well as the scarce compliance of patients to established strategies. Several nutraceuticals used in clinical practice have been shown to target the pathogenesis of diabetes mellitus, metabolic syndrome and their complications and to favorably modulate a number of biochemical and clinical endpoints. These compounds include antioxidant vitamins, such as vitamins C and E, flavonoids, vitamin D, conjugated linoleic acid, omega-3 fatty acids, minerals such as chromium and magnesium, alpha-lipoic acid, phytoestrogens, and dietary fibers. Several areas of concern exist regarding the use of dietary supplements and nutraceuticals in this setting, including product standardization, definition of optimal dosing regimen, potential side effects, drug interactions, and need for evidence-based indications.