Bronfenbrenner’s (1979) ecological model proposes that events in higher order social ecosystems should influence human development through their impact on events in lower order social ecosystems. This proposition was tested with respect to ecological violence and the development of children’s aggression via analyses of 3 waves of data (1 wave yearly for 3 years) from 3 age cohorts (starting ages: 8, 11, and 14) representing three populations in the Middle East: Palestinians (N = 600), Israeli Jews (N = 451), and Israeli Arabs (N = 450). Results supported a hypothesized model in which ethnopolitical violence increases community, family, and school violence and children’s aggression. Findings are discussed with respect to ecological and observational learning perspectives on the development of aggressive behavior.