This study examined treatment outcomes of 86 highly acculturated Hispanic and Anglo substance-abusing adolescents in functional family therapy, testing the hypothesis that ethnic matching of therapist and client is related to better treatment outcomes for clients. Adolescents reported on their substance use pre- and posttreatment on a timeline follow-back interview. Ethnically matched Hispanic adolescents demonstrated greater decreases in their substance use compared with Hispanic adolescents with Anglo therapists. Ethnic match status was not related to treatment outcome for Anglo clients. Thus, the matching hypothesis was supported for Hispanic clients only. The results underscore the importance of greater ethnic diversity among therapists and better cultural competency training for Anglo therapists. More research is needed on individual differences in the effects of ethnic matching.