Accumulating evidence suggests that the Dark Triad of personality (i.e., Narcissism, Psychopathy, and Machiavellianism) is useful in explaining individual differences in adult adjustment. The present study is among the first to examine unique effects of these traits on multi-informant ratings of adolescent aggressive behavior. In two samples (Ns= 611 and 302), we first established measurement invariance, internal consistency and validity of the 12-item Dirty Dozen Dark Triad measure. Furthermore, we found unique associations of each Dark Triad trait with particular forms of aggression, with inconsistent results across informants providing greater insight into these traits. Overall, Dark Triad traits seem applicable to adolescents and useful correlates of adolescent adjustment, especially if their unique effects are studied.