Background: To examine the potential mediating role of parenting behaviors in the longitudinal, bidirectional relationships between maternal depression and child internalizing symptoms (i.e. depression and anxiety). Methods: We analyzed data from 4,581 mother–child dyads from the Fragile Families and Child Wellbeing Study, assessed when the child was 3, 5, and 9 years old. Data included maternal depression diagnosis, child internalizing symptoms, and parenting behaviors (i.e. psychological aggression, nonviolent discipline, and physical assault). Data were analyzed using cross-lagged panel models. Results: Results indicated bidirectional relationships between maternal depression and child internalizing symptoms over childhood. Mediation analyses suggested that maternal depression led to subsequent increased psychological aggression toward their child, which in turn led to increased child internalizing symptoms. Nonviolent discipline and physical assault did not mediate this relationship. However, greater use of nonviolent discipline at age 5 among all parents predicted higher child internalizing symptoms at age 9. No parenting behaviors were both predicted by earlier child internalizing symptoms and predictive of subsequent maternal depression. Conclusions: Our results suggest a bidirectional relationship between child and maternal internalizing psychopathology that is partially explained by depressed mothers’ greater use of psychological aggression toward their children. It is important to note that the size of these effects were small, suggesting that the relationship between parent and child psychopathology is likely additionally explained by factors not assessed in the current study. Nonetheless, these results have implications for prevention and intervention strategies targeting child anxiety and depression.