This study provides a synthesis of meta-analyses and systematic reviews on non-pharmacological treatments for childhood aggression. Treatments referred to universal prevention, selective prevention, indicated prevention, or intervention (Mrazek and Haggerty, 1994). Seventy-two meta-analyses and systematic reviews met the inclusion criteria. We describe their characteristics, effect sizes across types of treatments, and the effects of various moderators. For universal and selective prevention, effects were mostly absent or small; for indicated prevention and interventions, effects were mostly small or medium. Only two moderators had a positive effect on treatment effectiveness, namely pre-test levels of aggression and parental involvement. These results identified similarities between indicated prevention and intervention treatments, on the one hand, and universal prevention and selective prevention, on the other. Our findings suggest that research distinguishing between targets of treatments (i.e., factors associated with childhood aggression vs. present aggressive behaviors) would be promising. Moreover, to further increase effectiveness of treatments for childhood aggression, individual differences warrant scientific attention.