Repeated or chronic stress has been implicated in the physiological dysregulation of multiple interrelated systems related to the stress response that, over time, may be a gateway for illness, disease, and premature aging. Much of this research has not been conducted on racially and socioeconomically diverse samples, likely underestimating the impact of environment on stress. This project examines the influence of individual and neighborhood-level characteristics on physiological dysregulation in a sample of African American and white adults in their middle years across 10 neighborhoods in Baltimore City. Data are from the National Institute on Aging study, Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS). The summary measure of physiological dysregulation (including indices of cardiovascular, metabolic, and immune function) was significantly higher for older adults and those with incomes below 125% of the federal poverty level. Negative binomial regression results showed that African American women had the highest levels of physiological dysregulation overall. Independent of individual-level characteristics, differences in physiological dysregulation were significantly associated with subjective and objective neighborhood characteristics. Physiological dysregulation tended to be lower for participants living in neighborhoods where they belonged to the majority racial group. Neighborhood collective efficacy, cooperative relationships among residents, had a significant inverse relationship with physiological dysregulation. These findings indicate that the ability to adapt to stressors over the life course is influenced by both individual and neighborhood-level characteristics. This research has benefits that extend to older adults who may be aging-in-place in their communities. A broader view of the ways in which social and physical environments meet the complex and varied needs of older adults is fundamental to the promotion of health, independence, and well-being in the later years.