This study investigated whether and how deficits in executive functioning and distortions in appraisal processing are related to subtypes of aggressive behavior. The sample included 83 boys assessed using multi-informant reports and performance measures. Deficits in two executive functions, response inhibition and planning ability were related primarily to reactive aggression. Hostile attributional biases moderated relations between planning ability and proactive and reactive aggression subtypes, with minimal relations between planning deficits and aggression at low levels of hostile attributional bias. As the level of hostile attributional bias increased, the relation between planning deficits and reactive aggression became increasingly large in a positive direction whereas the relation between planning deficits and proactive aggression became increasingly negative. Additionally, hostile encoding moderated the relation between behavioral inhibition and reactive aggressive behavior. Results also suggested a mediational role for response inhibition in the relation between planning ability and reactive aggression.