The present study examined the importance of psychopathy-linked narcissism in predicting proactive and reactive aggression and conduct problems in a group of 160 moderately to highly aggressive children (mean age of 10 years, 9 months). Children's self-report of self-esteem and parent and teacher report of dimensions of psychopathy [narcissism, callous–unemotional (CU) traits, and impulsivity], proactive and reactive aggression, and conduct problems were collected. Composites of parent and teacher ratings of children's behavior were used. Consistent with the study's hypotheses, narcissism predicted unique variance in both proactive and reactive aggression, even when controlling for other dimensions of psychopathy, demographic variables associated with narcissism, and the alternative subtype of aggression. As hypothesized, impulsivity was significantly associated with only reactive aggression. CU traits were not related to proactive or reactive aggression once the control variables were entered. All dimensions of psychopathy predicted unique variance in conduct problems. Consistent with prediction, narcissism was not significantly related to general self-esteem, providing support that narcissism and self-esteem are different constructs. Furthermore, narcissism and self-esteem related differentially to proactive aggression, reactive aggression, and conduct problems. Furthermore, narcissism but not self-esteem accounted for unique variance in aggression and conduct problems. The importance of narcissism in the prediction of aggressive behaviors and clinical implications are discussed. Aggr. Behav. 33:1–13, 2007. © 2007 Wiley-Liss; Inc.