Several studies provide evidence supporting a beneficial effect from the traditionalMediterranean diet (MedDiet) on the risk of type 2 diabetes mellitus (T2DM) and metabolic syndrome (MetS). This review summarizes the current scientific evidence from epidemiologic studies and clinical trials on the relation between the MedDiet and T2DM and MetS and the possible mechanisms underlying the reported associations. A recent meta-analysis of prospective cohort studies showed that greater adherence to the MedDietwas associated with a significant reduction in the risk of diabetes. The MedDiet has also been found to be beneficial in the prevention of gestational diabetes. Four large prospective studies have observed inverse associations between the MedDiet and MetS or its components. Few randomized controlled trials (RCTs) have evaluated the effect of th eMedDiet on T2DM and MetS. Results from the landmark PREvención con DIeta MEDiterránea (PREDIMED) nutrition intervention trial showed that participants assigned to the MedDiet had a significant30%reduction in the risk ofT2DMand that it also promoted the reversion of MetS and its components, hyperglycemia and central obesity. In addition, 5 RCTs showed the beneficial effects of the MedDiet comparedwith other dietary patterns on glycemic control in patients with T2DM. A recent meta-analysis of RCTs revealed that, compared with a variety of control diets, the MedDiet was associated with beneficial effects on all MetS components. Bioactive components of the MedDiet synergize to affect variousmetabolic pathways, leading to a reduced cardiometabolic disease risk. The abundance of healthy, nutrient-dense foods thatmakeup the plant-basedMedDiet predicts its bioactivity and potential to beneficially influence metabolic pathwaysthat lead to MetS and T2DM, aswell asother chronicconditions.Abundantepidemiologic andclinical trial evidence supports the role of the MedDiet on the prevention and management of T2DM and MetS.