Importance: The prevalence of hypertension and the risk for hypertension-related cardiovascular disease (CVD) are high among black adults. The population-attributable risk (PAR) accounts for both prevalence and excess risk of disease associated with a risk factor. Objective: To examine the PAR for CVD associated with hypertension among black adults. Design, Setting, and Participants: This prospective cohort study used data on 12497 black participants older than 21 years without CVD at baseline who were enrolled in the Jackson Heart Study (JHS) from September 26, 2000, through March 31, 2004, and cardiovascular events were adjudicated through December 31, 2015. The Reasons for Geographic and Racial Differences in Stroke (REGARDS) study participants were enrolled from July 1, 2003, through September 12, 2007, and cardiovascular events were adjudicated through March 31, 2016. Data analysis was performed from March 26, 2018, through July 10, 2019. Exposures: Normal blood pressure and hypertension were defined using the 2017 American College of Cardiology/American Heart Association blood pressure guideline thresholds. Main Outcomes and Measures: The PAR for CVD associated with hypertension, calculated using multivariable-adjusted hazard ratios (HRs) for CVD, coronary heart disease, heart failure, and stroke associated with hypertension vs normal blood pressure. Prevalence of hypertension among non-Hispanic black US adults 21 years and older without CVD was calculated using data from the National Health and Nutrition Examination Survey, 2011-2014. Results: Of 12497 participants, 1935 had normal blood pressure (638 [33.0%] male; mean [SD] age, 53.5 [12.4] years), 929 had elevated blood pressure (382 [41.1%] male; mean [SD] age, 58.6 [11.8] years), and 9633 had hypertension (3492 [36.3%] male; mean [SD] age, 62.0 [10.3] years). For a maximum 14.3 years of follow-up, 1235 JHS and REGARDS study participants (9.9%) experienced a CVD event. The multivariable-adjusted HR associated with hypertension was 1.91 (95% CI, 1.48-2.46) for CVD, 2.41 (95% CI, 1.59-3.66) for coronary heart disease, 1.52 (95% CI, 1.01-2.30) for heart failure, and 2.20 (95% CI, 1.44-3.36) for stroke. The prevalence of hypertension was 53.2% among non-Hispanic black individuals. The PAR associated with hypertension was 32.5% (95% CI, 20.5%-43.6%) for CVD, 42.7% (95% CI, 24.0%-58.4%) for coronary heart disease, 21.6% (95% CI, 0.6%-40.8%) for heart failure, and 38.9% (95% CI, 19.4%-55.6%) for stroke. The PAR was higher among those younger than 60 years (54.6% [95% CI, 37.2%-68.7%]) compared with those 60 years or older (32.0% [95% CI, 11.9%-48.1%]). No differences were present in subgroup analyses. Conclusions and Relevance: These findings suggest that a substantial proportion of CVD cases among black individuals are associated with hypertension. Interventions to maintain normal blood pressure throughout the life course may reduce the incidence of CVD in this population.