This study investigated behavioral and neural correlates underlying social feedback processing and subsequent aggressive behaviors in childhood in two age cohorts (test sample: n = 509/n = 385 and replication sample: n = 354/n = 195, 7-9 years old). Using a previously validated Social Network Aggression Task, we showed that negative social feedback resulted in most behavioral aggression, followed by less aggression after neutral and least aggression after positive feedback. Receiving positive and negative social feedback was associated with increased activity in the insula, medial prefrontal cortex and ventrolateral prefrontal cortex. Responding to feedback was associated with additional activation in the dorsolateral prefrontal cortex (DLPFC) following positive feedback. This DLPFC activation correlated negatively with aggression. Furthermore, age analyses showed that older children showed larger reductions in aggression following positive feedback and more neural activation in the DLPFC when responding to positive feedback compared to younger children. To assess the robustness of our results, we examined these processes in two independent behavioral/functional magnetic resonance imaging samples using equivalence testing, thereby contributing to replicable reports. Together, these findings demonstrate an important role of social saliency and regulatory processes where regulation of aggression rapidly develops between the ages of 7 and 9 years.