Purpose: The purpose of this paper is to examine the relationship between school climate and teacher stress. Specifically, the authors construct two parsimonious models to test two main hypotheses. First, whether preschool collegial leadership predicts teachers' job stress through the mediating role of teacher self-efficacy; second, whether teacher professionalism influences teachers' perceptions of occupational stress through the mediating role of teacher self-efficacy. Design/methodology/approach: The authors conceptualized the mediating role of teacher efficacy as an important mechanism that can help to explain the effect of school climate on teacher stress. School climate consisted of two dimensions: principal collegial leadership and professionalism. Therefore, the authors constructed and examined two mediation models by using Bootstrapping mediation modeling: first, preschool teacher self-efficacy as a mediator between preschool collegial leadership and teacher stress; second, preschool teacher self-efficacy as a mediator between preschool teacher professionalism and teacher stress. Findings: Results from two mediation analyses showed that principal collegial leadership exerts a significant negative effect on preschool teachers' stress through the mediating role of teacher self-efficacy. Moreover, professionalism was also a significant predictor of preschool teachers' stress through the mediating role of teacher self-efficacy. Research limitations/implications: This study contributes to the literature in terms of understanding the mechanism of how school climate helps to reduce teacher stress. First, the authors found that teachers' individual well-being can be efficiently enhanced through a more collegial leadership. Second, the preschool leadership teams can create a supportive climate to reduce teachers' stress by improving teachers' professionalism. Originality/value: This study offers a new perspective about understanding the internal and external mechanism of teacher stress. The authors discussed the results in light of the recent push by the Chinese Government to teacher quality improvement in early childhood education. The authors argued for prioritizing support for building a supportive school climate for teachers.