Objective: The prevention of delinquency can have long-term benefits for both the individual and society. Previous work has demonstrated positive effects of Treatment Foster Care Oregon (TFCO) on reducing delinquency across a 2-year period for adolescent females involved in the juvenile justice system. The present study examined whether the effects of TFCO are present across a 10-year period, and whether criminal offenses accrued in the juvenile justice system mediate the association between intervention condition and cumulative criminal offenses through emerging adulthood. Method: The sample included 166 women (68% non-Hispanic White) who had been court mandated to out-of-home care as adolescents, randomly assigned to one of two interventions, and followed for an average of 10 years. Juvenile (< 18 years of age) and adult criminal records data were collected and coded for offense severity. Results: Analyses revealed a significant effect of the TFCO intervention on cumulative criminal offense charge severity across the 10-year follow-up period ([beta] = -0.15, p < 0.05). This effect was mediated by offense charges that occurred after the baseline assessment and prior to Age 18, as shown through a significant indirect effect, [beta] = -0.09, p < 0.05, suggesting the importance of reductions in juvenile delinquency on later criminal offending. Conclusions: Intensive out-of-home interventions that reduce juvenile offenses for youth with chronic delinquency may have sustained effects on adult criminality. Implications for prevention programs for female adolescents are discussed. [This is the online first version of an article published in "Journal of Consulting and Clinical Psychology" (ISSN 0022-006X).]