This study aimed to investigate the effects of shyness of 3 to 5-year-olds and the teacher-child relationship on peer play behaviors. For this purpose, a survey was conducted targeting 33 teachers working with 277 three to five-year-olds at child care centers located in Chungbuk, Korea. SPSS 19.0 was used to implement exploratory analyses and hierarchical regression analysis. It was found that children with low sociability and thoes with close relationships with teachers indicated the least play disruption. Children whose assertiveness and sociability were low and whose relationships with teachers were close were likely to do the most play interaction. However, regardless of the level of the lack of assertiveness and of the lack of sociability, children with close relationships with teachers had a higher level of play interaction. Children with a higher level of lack of sociability and in conflict relationships with teachers had a higher level of play disconnection. Findings of this study highlight the importance of considering the interplay of children’s shyness and teacher-child relationships in the development of peer play behaviors.