Numerous studies have focused on the role of neighborhood socioeconomic status in childhood obesity and physical activity, but few studies have examined the effect of neighborhood socioeconomic changes over time and the interaction between family and neighborhood SES on childhood obesity and physical activity. This study measured neighborhood socioeconomic histories between 2000 and 2010 and examined the associations between neighborhood socioeconomic histories and childhood obesity, as well as physical activity. The moderating role of family poverty status was also examined. Using the Healthy Communities Study (2013-2015), we measured obesity indicators (objectively measured body mass index z-score and waist circumference) and a physical activity indicator (self-reported moderate-to-vigorous physical activity) for a cohort of 4114 children. Multilevel linear regression models were used to examine the associations between neighborhood socioeconomic histories between 2000 and 2009-2013 and body-mass index z-score, waist circumference, and moderate-to-vigorous physical activity. Results showed that higher-income children in consistently high socioeconomic neighborhoods had lower measured BMIz and WC and engaged in more moderate-to-vigorous physical activity than higher-income children in consistently low socioeconomic neighborhoods. Additionally, low-income children in consistently moderate socioeconomic neighborhoods reported a lower level of moderate-to-vigorous physical activity than low-income children in consistently low socioeconomic neighborhoods. The findings indicate that considering both family and neighborhood socioeconomic status may help elucidate the underlying differences in childhood obesity and physical activity levels by socioeconomic status.