Economic exchange games have rarely been applied to examine psychopathology in youth. In the current study we adapted a trust game to investigate the relations between externalizing behavior problems, trust, and trustworthiness. We were particularly interested in the differential modulating impact of "known identity" (vs. anonymous) condition of the task. Second, we examined whether anomalies in trust behavior would correspond to social cognition manifested in children with externalizing problems. A total of 171 (79 age-matched pairs) boys (mean age = 12.84; SD = 1.80) were recruited from community groups where social networks and relationships amongst peers have been established. A trust game was played under two conditions: an anonymous version where the identity of the trust game partner was not known and a "known identity" version where identities were revealed. Results supported the conclusion that boys with externalizing behavior problems are generally less trustworthy, but not less trusting and that this was true especially for the known identity version of the game. Moreover, anomalies in trust behavior were associated with hostile intentions, but not reflective of a general theory of mind deficit. This study contributes to an emerging literature using economic exchange games to investigate real-time, real-life exchanges in relation to psychopathology.