Background: Characteristics associated with low socioeconomic status neighbourhoods may put children at risk for unique chronic stressors that affect cortisol levels. This research sought to explore whether neighbourhood stressor exposure affected serum cortisol levels among children. Methods: A total of 148 African and European-American children with an average age of 8.28 years participated in a longitudinal study evaluating ethnic differences in body composition and disease risk. Five waves of data were included in analyses. Mixed modelling was used to explore neighbourhood stressors, which was a composite index of five items for zip code level poverty and physical disorder, and serum cortisol outcomes for the full sample, by race/ethnicity and gender. Adjustments were made for individual level correlates age, pubertal status, gender and total fat mass. Results: Neighborhood disorder was predictive of lower serum cortisol levels among African-American children (p<0.05), such that higher neighbourhood stressor exposure resulted in lower serum cortisol over time compared with individuals in socially ordered neighbourhoods. Neighbourhood disorder was marginally significant and predictive of higher serum cortisol among European-American children (p<0.10). Transition to a higher pubertal status, nested in age was also predictive of lower serum cortisol levels (p<0.01) among European-American children. Conclusion: Children who are exposed to negative socioenvironmental climates over time are more likely to have altered serum cortisol levels. This may be an adaptive mechanism to cope with stress; however, disrupted cortisol levels may have negative effects on general physical and mental health.