Investigated how maternal depression influenced the relation between mothers' perceptions of the quality of their partner interactions and behavior problems among their preschool children. Participants included 194 low-income families from 4 sites. Approximately three fourths of the mothers (72%, n = 139) identified a male partner and comprised the analysis sample. Mothers were adolescents (< or = age 19) at delivery, and data were gathered when children were 4 to 5 years of age. In this high-risk sample, 42.4% of the children had been maltreated, 36% had externalizing scores in the clinical range, and 10.8% had internalizing scores in the clinical range. Multiple regression analyses revealed (a) maternal perceptions of negative partner interactions were associated with more internalizing behavior problems among the children, adjusting for the effects of maltreatment; (b) maternal depression mediated the relation between the maternal perceptions of the quality of partner interactions and children's internalizing and externalizing behavior problems; and (c) maternal perceptions of positive partner interactions did not protect children from internalizing or externalizing behavior problems associated with maltreatment. Programs for adolescent mothers should provide screening and treatment for depressive symptoms and help partners negotiate caregiving roles and mutually satisfying relationships.