This study investigated the mediating effects of professional learning community (PLC) components on the relationship between leadership practices and teacher collective efficacy from the perspective of Chinese principals. Survey data were collected from 878 school principals. The results revealed that leadership practices significantly and positively affected the five PLC components, three of which (shared purpose, collective focus on student learning and reflective dialogue) had significant positive effects on teacher collective efficacy. Shared purpose, collective focus on student learning and reflective dialogue significantly mediated the effects of leadership practices on teacher collective efficacy. The practical implications of the findings and suggestions for future research are discussed.