The current project aims to explore the connection between maternal depression and offspring aggression during the transition to adulthood. Although several studies have established a link between maternal depression and offspring aggression in childhood and early adolescence, it is not known whether this association persists into adulthood. In addition, it is not known whether this risk is observable across multiple forms of aggression or what mechanisms account for this increased risk. The analyses presented here suggest that maternal depression confers a risk for higher levels of aggressive behavior by offspring at age 20. In two of the domains studied (intimate partner violence and relational aggression), this risk appeared to be specific to female offspring, although both sons and daughters showed elevated levels of general physical aggression. Results from Structural Equation Models suggest that the association between maternal depression and youth aggression is fully mediated by youth history of depression by mid-adolescence. Marital conflict, parent-child relationship quality, and youth social functioning were not unique mediators of this relationship. The limitations and implications of these findings are discussed.