The 2017 American College of Cardiology/American Heart Association (ACC/AHA) high blood pressure (BP) guideline lowered the cut-off for hypertension, but its age-specific association with cardiovascular disease (CVD) remains inconclusive in different populations. We evaluated the association between high BP according to the 2017 ACC/AHA guideline and CVD risks in Koreans aged 20–94 years. In a nationwide health screening cohort, we included 15,508,537 persons aged 20–94 years without prior CVD. BP was categorized into normal, elevated, stage 1 hypertension, or stage 2 hypertension. The primary outcome was a composite CVD hospitalization (myocardial infarction, stroke, and/or heart failure). Over 10 years of follow-up, CVD incidence rates per 100,000 person-years were 105.4, 168.3, 215.9, and 641.2 for normal, elevated BP, stage 1, and stage 2 hypertension, respectively. The age-specific hazard ratios of stage 1 hypertension compared to normal BP were 1.41 (1.34–1.48) at ages 20–34, 1.54 (1.51–1.57) at ages 35–49, 1.38 (1.35–1.40) at ages 50–64, 1.21 (1.19–1.24) at ages 65–79, and 1.11 (1.03–1.19) at ages 80–94 years. With the lowered BP cut-off, 130/80 mmHg, population attributable fraction for CVD was 32.2%. In conclusion, stage 1 hypertension was significantly associated with a higher CVD risk across entire adulthood. The new definition of hypertension may have a substantial population impact on primary CVD prevention.