In the Dietary Approach to Stop Hypertension (DASH) trial, the DASH diet reduced blood pressure (BP) in a diverse sample of US adults. Subsequent analyses of this trial documented the efficacy of the DASH diet in several subgroups. Although subgroup analyses in individuals with metabolic syndrome (MS) have not been performed, the DASH diet has been recommended in MS patients. This paper is a subgroup analysis of the DASH trial, in which we examined the effect of study diets on BP in participants with and without MS. Participants were stratified according to MS status (99 with MS, 311 without MS (Non-MS)). The trial was a dietary intervention study in which participants were randomized to receive a control diet, a diet rich in fruits and vegetables, or the DASH diet. Outcomes were (i) the difference in BP between the end and the beginning of intervention and (ii) control of hypertension. We found no significant interaction between MS status and diet assignment on BP (each P-interaction >0.05). In the MS subgroup, the DASH diet compared with the control diet reduced systolic BP by 4.9 mm Hg (P=0.006) and diastolic BP by 1.9 mm Hg (P=0.15). In the Non-MS subgroup, corresponding net BP reductions were 5.2 mm Hg (P<0.001) and 2.9 mm Hg (P<0.001), respectively. The DASH diet controlled hypertension in 75% of hypertensive participants with MS (adjusted odds ratio=9.5 vs the control diet, P=0.05). In conclusion, the DASH diet similarly reduces BP in those with and without MS. Our findings provide direct evidence for existing recommendations.