This paper reports findings from an exploratory outcome study of the Program for Young Negotiators training model with early adolescents in Buenos Aires, Argentina. Youth between the ages of 10 and 15 years (135 females, 70 males) were assessed before and after negotiation training, based on two measures of psychosocial attitudes and behavior. On the Five Factor Negotiation Scale (Nakkula & Nikitopoulos, 1999a), an increase in overall negotiation attitudes and behavior was found, with particularly large increases in the domains of conflict-based perspective taking and behavioral approaches to conflict resolution. On the Relationship Questionnaire, Schultz and Selman's (1999) structural developmental measure of psychosocial competence, stronger than expected changes were found in overall competence, with fairly equal changes in the primary domains of interpersonal understanding, interpersonal skills, and the personal meaning of relationships. Finally, students who presented a pretest thought-action gap marked by a high level of interpersonal understanding relative to their level of interpersonal skill increased substantially more in negotiation attitudes and behavior than did students manifesting a gap in the opposite direction. Implications regarding who benefits most from negotiation training are discussed.