This study evaluated multiple facets of self-perceptions that have been theorized and shown to play a contributory role in the development of aggression for less clinically severe populations in a sample of youths from the juvenile justice system. Independent and unique associations of low self-esteem and inflated self-perceptions with aggression were examined in a sample of male juvenile offenders (N = 119; Mean age = 16.74 years) using a longitudinal study design. Latent growth curve modeling analyses revealed that self-esteem, adaptive and maladaptive narcissism independently predicted juvenile offenders' initial levels of aggression. It was also found that perceptual bias independently predicted changes in aggression over time. With the inclusion of all variables in the same model, self-esteem was no longer associated with aggression; however, all other relationships remained significant. The implications of these findings as well as the importance of interventions targeting self-perceptions to decrease aggression among high-risk youths are discussed.