The effects of grape-seed polyphenols against the development of hypertension and other cardiometabolic conditions associated with the metabolic syndrome (MetS) were studied in rats fed a high-fat, high-carbohydrate diet, known as the cafeteria (CAF) diet. Two groups of Wistar rats were fed standard (STD) or CAF diets for 12 weeks. The CAF diet-fed rats were administered different doses of a low-molecular-weight grape-seed polyphenol extract (LM-GSPE) (25, 100 and 200 mg/kg per d) or vehicle daily, and the STD diet-fed rats were administered LM-GSPE (100 mg/kg per d) or vehicle using ten animals per group. Body weight (BW), waist perimeter (WP) and systolic and diastolic blood pressures (BP) by the tail-cuff method were recorded weekly. The animals were housed in metabolic chambers every 2 weeks to estimate daily food and liquid intakes and to collect faeces and urine samples. The plasma lipid profile was analysed at time 0 and on the 4th, 7th, 10th and 12th weeks of the experiment. Moreover, plasma leptin was measured at the end of the experiment. Results demonstrated that LM-GSPE, when administered with the CAF diet, attenuated the increase in BP, BW, WP and improved lipid metabolism in these animals. However, although the 25- and 100-mg/kg per d doses were sufficient to produce beneficial effects on BP and lipid metabolism, a 200-mg/kg per d dose was necessary to have an effect on BW and WP. The present findings suggest that LM-GSPE is a good candidate for a BP-lowering agent that can also ameliorate other conditions associated with the MetS.