Abstract Body: Ambulatory blood pressure monitoring (ABPM) is an assessment method in which BP measurements are taken at regular intervals when individuals are awake and asleep, during a typical 24-hour period. Thus, ABPM is an accurate and effective way to measure BP. Neighborhood social and built environments play an important role in health, which were previously associated with cardiovascular risk factors. However, the effects of neighborhood social and built environments on ABPM is understudied, particularly among young adults and African Americans. The current study aimed to investigate the cross-sectional associations between neighborhood social and built environments and ABPM in our Georgia Stress and Heart Cohort consisting of 543 participants, aged 29.1 ± 3.6 years, 49.7% African American and 51.2% female. There were found to be consistent positive associations of neighborhood social and built environments with 24-hour systolic BP (SBP), 24-hour diastolic BP (DBP), daytime SBP, daytime DBP, nighttime SBP, and nighttime DBP (p≤0.01, respectively), after the adjustment for age, race and sex. Neighborhood factors such as Median Household Income and College Graduation held the negative associations with measurements of 24-hour SBP, 24-hour DBP daytime SBP, daytime DBP, nighttime SBP, nighttime DBP, and 24-hour SBP (p≤0.01, respectively). This study is one of the first to report the relationship between neighborhood social and built environments and ABP, particularly in young adults and African Americans residing in the US southeastern region. Future longitudinal studies are warranted to further support the findings of the current study.