Black pepper is used worldwide to enhance food flavor. We investigated dietary supplementation with piperine, the active principle of black pepper, to high carbohydrate, high fat (HCHF) diet-fed rats as a model of human metabolic syndrome. Rats were fed with either HCHF diet (carbohydrate, 52%; fat, 24%; 25% fructose in drinking water) or cornstarch (CS) diet for a total of 16 weeks. Diets of the treatment groups (CS + piperine and HCHF + piperine) were supplemented with piperine for the last 8 weeks of this protocol. After 16 weeks, rats fed with HCHF diet developed hypertension, elevated oxidative stress and inflammation-induced cardiac changes (infiltration of inflammatory cells in heart, increase in count and degranulation of mast cells in heart, cardiac fibrosis and increase in ventricular stiffness), reduced responsiveness of aortic rings, impaired glucose tolerance, abdominal obesity together with liver fibrosis, fat deposition and increased plasma liver enzymes. Supplementation with piperine (375 mg/kg food; approximately 30 mg/kg/day) in HCHF-fed rats normalized blood pressure, improved glucose tolerance and reactivity of aortic rings, reduced plasma parameters of oxidative stress and inflammation, attenuated cardiac and hepatic inflammatory cell infiltration and fibrosis and improved liver function. These changes clearly suggest that piperine reduces symptoms of human metabolic syndrome in HCHF-fed rats by reducing inflammation and oxidative stress.