The purpose of the study was to analyze the effects of both young children's gender and temperament and their teachers' teaching efficacy and teacher-child interactions on peer play interactions. For this purpose, the data from the 2012 Panel Study on Korean Children were analyzed using analyses of variances and correlation co-efficiencies. In addition, analyses of hierarchical regression, with young children's temperament and teacher-related factors (teaching efficacy and teacher-child interactions) as the independent variables and three sub-factors of peer play interactions (play interaction, play disruption, play disconnection) as the dependent variables, were conducted. The results showed that young children's temperament, teacher efficacy, teacher-child interactions, and peer play interactions differed by gender and significantly correlated. Young children’s temperament and teacher-child interactions significantly affected young children's peer play interactions, and the effect of teacher-child interactions was larger than the effect of temperament by 2~2.5 times. The results proved the importance of early childhood teachers' roles in the development of young children's peer interactions with consideration of differences based on children's gender and temperament. With the results given, implications and suggestions for further research were discussed.