Previous research has found an association between mothers' depressive symptoms and their adolescents' involvement in aggression. The present study examined three mechanisms believed to account for this relation: parenting practices, family functioning, and informant discrepancy. Participants were a high-risk sample of 927 mother-adolescent dyads (66% African American) who completed baseline assessments for the Multisite Violence Prevention Project. Maternal depressive symptoms were assessed using the Center for Epidemiologic Studies Depression scale. Adolescents' aggression was assessed using parent- and teacher-report on the Behavior Assessment System for Children and student-report on the Problem Behavior Frequency Scale. Mothers' reports of depressive symptoms were significantly related to their adolescents' aggression based on student, teacher, and mothers' reports, with the strongest correlations found with mothers' reports. Multilevel modeling indicated that maternal depressive symptoms were related to the degree of discrepancy between mothers' ratings of their adolescents' aggression and ratings by adolescents and their teachers. Smaller discrepancies between mothers' and teachers' ratings of adolescents' aggression were found for depressed mothers, as compared to non-depressed mothers. Structural equation models indicated that the relation between maternal depressive symptoms and mothers' report of adolescents' aggression was mediated by several parenting and family functioning variables, with the clearest effects for parenting practices. Similar findings were not found in analyses predicting adolescents' ratings and teachers' ratings. These findings underscore the potential direct and indirect benefits of interventions focused on reducing depression among mothers with adolescent children.