This study used data from the Project on Human Development in Chicago Neighborhoods, a multilevel, longitudinal study of children sampled from 80 diverse neighborhoods, to explore associations among changes in neighborhood poverty from 1990 to 2000 and changes in youth's internalizing problems and property and violent offenses over 6 years (N = 3,324; mean age across waves = 12.6 years). After accounting for a host of background characteristics and weighting for the propensity to stay in the original sampled neighborhood, results indicated that neighborhood poverty dynamics were unfavorably linked to boys' problem behaviors. In high-poverty (>30% in 1990) neighborhoods, decreasing poverty was associated with boys' greater internalizing problems and higher probability of increasing in violent behavior than stable neighborhood poverty. In moderate-poverty (20%-30% in 1990) neighborhoods, boys in neighborhoods that got poorer had more internalizing problems than boys in stably poor neighborhoods. Likewise, in low-poverty (<20% in 1990) neighborhoods, increasing poverty was associated with boys' higher probability of increasing in violent behavior than stable neighborhood poverty. Effect sizes were larger in high- and moderate-poverty neighborhoods than in low-poverty neighborhoods. This study complements the neighborhood mobility literature and has implications for interventions aimed at community revitalization.