This study obtained teacher ratings of impulsivity, callous-unemotional traits, narcissism, and Machiavellianism for a sample of 252 middle school children, and investigated the extent to which these variables were related to reactive versus proactive aggression and physical versus relational aggression. Results showed a main effect for gender, with boys rated highest on all measures of psychopathy and aggression, with the exception of relational aggression. Results of hierarchical multiple regressions showed that whereas impulsivity was associated with all types of aggression, CU traits, narcissism, and Machiavellianism were differentially related to specific forms of childhood aggression. In addition, Machiavellianism mediated the relationship between narcissism and relational aggression. Implications for fine-tuning interventions in ways that account for the motivators underlying subtypes of childhood aggression are discussed.