Objectives: This study examined the links between maltreatment, posttraumatic stress symptoms, ethnicity-specific factors (i.e., perceived discrimination, ethnic identity, and ethnic orientation), and alcohol and/or other drug (AOD) problems among adolescent girls. Methods: These relations were examined using archived data from a community sample of 168 Black and Hispanic adolescent girls who participated in a school-based substance use intervention. Results: The results revealed that maltreatment was linked to AOD problems, but only through its relation with posttraumatic stress symptoms; maltreatment was positively related to posttraumatic stress symptoms, which were positively related to AOD problems. Both perceived discrimination and ethnic orientation were significant moderators. Specifically, greater perceived discrimination was associated with an increased effect of maltreatment on posttraumatic stress symptoms. Ethnic orientation demonstrated protective properties in the relation between maltreatment and AOD problem severity, such that the effect of maltreatment on AOD problem severity was less for girls with average to high ethnic orientation compared to girls with low ethnic orientation. Conclusions: The findings of this study underscore the importance of developing interventions for Black and Hispanic girls that target maltreatment and AOD use concurrently and address ethnicity-specific factors. (Contains 2 tables and 4 figures.)