This study examined whether the relation between maladaptive emotion regulation and aggression was mediated by deviant social information processing (SIP). Participants were 193 preschool children. Emotion regulation and aggression were rated by teachers. Deviant SIP (i.e., attribution of hostile intent, aggressive response generation, aggressive response evaluation and decision) was measured from children's responses to hypothetical social conflicts. Findings revealed that the relation between maladaptive emotion regulation and aggression was direct and not mediated by SIP biases (i.e., aggressive response generation, aggressive response evaluation and decision). Results are discussed from a theoretical and methodological perspective.