The current study assessed 1) whether there are bidirectional associations between parent-reported parent-to-child and/or child-to-parent internalizing psychopathology from middle childhood to preadolescence, 2) if child-reported parental acceptance/warmth moderates bidirectional associations, and 3) if bidirectional associations vary by parent-child sex dyad. A sample of 11,878 9/10-year-old children (48% female) at the baseline of the Adolescent Brain Cognitive Development (ABCD) study and follow-up two years later (N=6,552) completed child-report parental acceptance/warmth and parent-report children’s and parents’ internalizing psychopathology measures. Path analysis revealed 1) significant, yet small, parent-to-child and child-to-parent bidirectional associations of internalizing psychopathology, 2) parental acceptance/warmth neither moderated parent-to-child nor child-to-parent bidirectional associations, and 3) the most parsimonious model constrained parent-child sex dyad bidirectional associations to equality. These results suggest additional risk is conferred by longitudinal parent-to-child and child-to-parent transmission that is not accounted for by concurrent associations between parents’ and children’s internalizing problems or stability of internalizing problems across time.