The present study investigated the structural relationships between Korean preschool teachers' work environments, self-efficacy, and children's peer play interactions; it also examined the mediating influence of teacher-child interactions on these relationships. This study performed SEM analysis on 1193 teachers' survey responses from the 2014 Panel Study on Korean Children. The results showed that, first, teachers' self-efficacy not only directly influenced teacher-child interactions but also influenced children's peer play interactions through teacher-child interactions. Second, teachers' work environments not only directly influenced teacher-child interactions, but also influenced children's peer play interactions (mediated by teacher-child interactions). Third, teacher-child interactions had a direct effect on children's peer play interactions. The paper concludes with a discussion of the implications of the influence of Korean preschool teachers' work environments and self-efficacy on children's peer play interactions, mediated by teacher-child interactions.