BackgroundChildren who are not accepted in their peer group are at risk of developing internalizing problem behaviors. It is possible, however, that supportive parenting can provide a buffer against the detrimental effects of low peer acceptance.ObjectiveThis study examined maternal and paternal affection and psychological control as moderators of the association between children’s peer acceptance during the critical transition to primary school and level and subsequent development of internalizing problem behaviors from first to sixth grade.MethodA total of 608 children (264 girls, 344 boys) were rated by their teachers on their internalizing problems in grades 1, 2, 3, 4 and 6. Children’s peer acceptance was measured in the first grade using a sociometric nomination procedure. At the same time point, mothers (n = 432) and fathers (n = 281) completed questionnaires measuring their levels of affection and psychological control.ResultsThe results of latent growth curve modelling showed, first, that on average children’s internalizing problems decreased over the school years. Second, peer acceptance was associated with the development of internalizing problems: the higher the peer acceptance, the bigger the decrease—and the lower the peer acceptance, the smaller the decrease—in the level of internalizing problems across time. However, high maternal affection provided a buffer against this impact of low peer acceptance. Among boys, low levels of maternal psychological control also provided a buffer against the effects of low peer acceptance. No significant results were found on the moderating role of fathers’ parenting styles.ConclusionOverall, the results suggested that mothers’ emotionally sensitive and supporting caregiving may protect children from the harmful long-term effects of low peer acceptance.