PURPOSE The purpose of this study was to investigate the effects of 8-week aerobic exercise and polyphenol intake on body composition, cardiovascular response, vascular endothelial function, and physical fitness at rest and during exercise in prehypertensive men. METHODS The study included twenty-eight males in their 20-30 years of age with prehypertension. Participants in the aerobic exercise + polyphenol intake group (EX + PP; <i>n</i> = 14) performed aerobic exercise three sessions/week, 30 min/session, at 65% of the heart rate reserve, and consumed polyphenol (grape seed extract 300 mg) for 8 weeks. Participants in the aerobic exercise + placebo intake group (EX + PL; <i>n</i> = 14) performed the same aerobic exercise; however, they consumed placebo instead of polyphenol. All independent variables were measured at pre-test and post-test, and the data were analyzed. RESULTS The main results of the study were as follows: 1) SBP and MAP at rest decreased significantly in EX + PP, while MAP decreased significantly in EX + PL group. 2) In the EX + PP group, CO increased significantly, whereas DBP, MAP, and TPR decreased significantly during the hand grip exercise. In contrast, CO decreased significantly, while DBP and TPR increased significantly in the EX + PL group during the hand grip exercise. 3) Regarding vascular endothelial function, % FMD increased significantly in EX + PP group. 4) Sit-up increased significantly in both EX + PP and EX + PL groups; however, sit-and-reach in EX + PP group was significantly higher than that in EX + PL group at post-test. CONCLUSIONS The findings of this study showed that the 8-week aerobic exercise would have positive effects on body composition, cardiovascular response, and physical fitness at rest and during exercise in hypertensive men. Additionally, polyphenol intake would contribute more towards reduction of blood pressure at rest and during exercise and improvement of vascular endothelial function.