Abstract Objective Specific parental behaviors and cognitions are associated with child anxiety. Studies informing us of the directionality of the associations are lacking. We investigated the effect of parental involvement in children's anxiety treatment on parental behaviors and cognitions. Method Children (N=54, 7–12 years) and parents were randomly allocated to different treatment groups (involved, not involved). Observed behavior, self-reported behavior and cognitions were assessed separately for mothers and fathers at pre-, posttreatment and follow-up. Results There were no differences over time for self-reported parental efficacy and observed negativity, but self-reported autonomy granting increased for both groups over time. Differential effects were found between groups for observed paternal over-involvement (fathers involved in treatment showed a more rapid decrease) and self-reported maternal autonomy-granting (non-involved mothers showed a greater increase). Conclusion Our findings suggest that child anxiety significantly influences parental behaviors and cognitions. Child therapy may successfully change the family system.