In a survey among 360 parent-child dyads (children aged 8–12 years), parent and child reports of parental advertising mediation activities were examined. The first aim was to investigate how parent-child agreement in reporting mediation differed by family and child factors. Results showed that agreement was highest in communication-oriented families and between parents and girls. The second aim was to examine the role of agreement in predicting the mediation outcome (i.e., reduced materialism). Both measures predicted the mediation outcome, but its effectiveness was contingent on parent-child agreement. Mediation was most effective when parents and children both reported that parents often discussed advertising.