Abstract Background and Aims Flow-mediated dilatation of the brachial artery (FMD) is a biomarker of endothelial function and cardiovascular health. Impaired FMD is associated with several cardiovascular risk factors including hypertension and obesity. Various food ingredients such as polyphenols have been shown to improve FMD. We investigated whether consuming resveratrol, a polyphenol found in red wine, can enhance FMD acutely and whether there is a dose-response relationship for this effect. Methods and Results 19 overweight/obese (BMI 25–35 kg m−2 ) men or post-menopausal women with untreated borderline hypertension (systolic BP: 130–160 mmHg or diastolic BP: 85–100 mmHg) consumed three doses of resveratrol (resVida™ 30, 90 and 270 mg) and a placebo at weekly intervals in a double-blind, randomized crossover comparison. One hour after consumption of the supplement, plasma resveratrol and FMD were measured. Data were analyzed by linear regression versus log10 dose of resveratrol. 14 men and 5 women (age 55 ± 2 years, BMI 28.7 ± 0.5 kg m−2 , BP 141 ± 2/89 ± 1 mmHg) completed this study. There was a significant dose effect of resveratrol on plasma resveratrol concentration ( P  < 0.001) and on FMD ( P  < 0.01), which increased from 4.1 ± 0.8% (placebo) to 7.7 ± 1.5% after 270 mg resveratrol. FMD was also linearly related to log10 plasma resveratrol concentration ( P  < 0.01). Conclusion Acute resveratrol consumption increased plasma resveratrol concentrations and FMD in a dose-related manner. This effect may contribute to the purported cardiovascular health benefits of grapes and red wine.