Executive function (EF) has been implicated in childhood aggression. Understanding of the role of EF in aggression has been hindered, however, by the lack of research taking into account the function and form of aggression and the almost exclusive focus on cool EF. This study examined the role of cool and hot EF in teacher reported aggression, differentiating between reactive and proactive as well as physical and relational aggression. Children (N = 106) completed laboratory tasks measuring cool (inhibition, planning, working memory) and hot EF (affective decision-making, delay of gratification). Cool, but not hot, EF significantly contributed to understanding of childhood aggression. Inhibition was a central predictor of childhood aggression. Planning and working memory, in contrast, were significant independent predictors of proactive relational aggression only. Added to this, prosocial behaviour moderated the relationship between working memory and reactive relational aggression. This study therefore suggests that cool EF, particularly inhibition, is associated with childhood aggression across the different functions and forms.