BACKGROUND: Nocturnal blood pressure (BP) is associated with risk for cardiovascular events. However, the relationship between nocturnal BP in young adults and cognitive function in midlife remains unclear. METHODS: We used data from the ambulatory BP monitoring substudy of the Coronary Artery Risk Development in Young Adults Study, including 224 participants (mean age 30 years, 45% men, 63% African Americans). At the 20-year follow-up, the Stroop test (executive function), Digit Symbol Substitution Test (psychomotor speed), and Rey Auditory Verbal Learning Test (verbal memory) were assessed. RESULTS: Baseline mean office, daytime, and nocturnal BP were 109/73, 120/74, and 107/59 mm Hg, respectively. Nocturnal BP dipping, calculated as (nocturnal systolic BP [SBP]--daytime SBP) × 100/daytime SBP, was divided into quartiles (Q1: -39.3% to -16.9%; Q2: -16.8% to -13.2%, Q3 [reference]: -13.1% to -7.8%, and Q4: -7.7% to +56.4%). In multiple regression analyses, the least nocturnal SBP dipping (Q4 vs. reference) and higher nocturnal diastolic BP level were associated with worse Stroop scores, with adjustments for demographic and clinical characteristics, and cumulative exposure to office BP during follow-up (β [standard error]: 0.37 [0.18] and 0.19 [0.07], respectively; all P < 0.05). Digit Symbol Substitution Test and Rey Auditory Verbal Learning Test were not significantly associated with nocturnal SBP dipping or nocturnal SBP/diastolic BP levels. CONCLUSIONS: Among healthy young adults, less nocturnal SBP dipping and higher nocturnal diastolic BP levels were associated with lower executive function in midlife, independent of multiple measures of office BP during long-term follow-up.