The Youth Psychopathic Traits Inventory (YPI) is a self-report measure of juvenile psychopathic traits. Validity data for this measure are limited, especially for nonreferred samples. This report investigated the concurrent validity of the YPI by assessing 171 nonreferred male youth (M age = 12.96 years) with a battery of self-, parent-, and peer-report measures including the Child Behavior Checklist (CBCL), the Reactive-Proactive Aggression Questionnaire (RPQ), the Antisocial Process Screening Device (APSD), and a peer-sociometric measure of aggression. Results confirmed the expected correlations between the YPI and measures of proactive aggression, other externalizing and internalizing behavior, and parent-report psychopathic-like traits. In addition, cluster analyses of YPI scores revealed 2 groups of youth (low vs. high) who scored differently on measures of externalizing behavior. This study supports the utility of the YPI as a research tool for assessing juvenile psychopathic traits.