The purpose of this study is to investigate the moderating effect of mother’s discipline style on the relationship between young children’s difficult temperament and young children’s peer interaction. To verify this, 307 mothers with 36-72 months of young children were asked to measure their difficult temperament, peer interaction, and mother’s discipline. The results of this study are summarized as follows. First, young children’s difficult temperament showed a significant negative correlation with young children’s peer interaction, the mother’s positive discipline showed a significant positive correlation with young children’s peer interaction, and the mother’s negative discipline showed a significant negative correlation with young children’s peer interaction. Second, young children’s difficult temperament was found to affect young children’s peer interaction. Third, mother’s positive and negative discipline had an effect on young children’s peer interaction. Fourth, the moderating effect of mother’s positive discipline style was proved in the relationship between young children’s difficult temperament and young children’s peer interaction. Fifth, the moderating effect of mother’s negative discipline style was proved in the relationship between young children’s difficult temperament and young children’s peer interaction. Based on these, the implications and limitations of this study and the direction of follow-up research were discussed.