This paper examines the influence of professional learning communities (PLCs) on informal teacher leadership in Hong Kong schools to overcome issues reported in the literature on the challenges to teacher leadership posed by Chinese hierarchical school contexts. We test the relations among PLC, informal teacher leadership, teacher focus on improving student learning, principal instructional leadership, and middle leadership (e.g., subject heads) with structural equation modeling of survey responses from 638 teachers of primary and secondary schools in Hong Kong. The results show an overall positive influence among all factors in the study. PLCs have the highest positive influence among the factors considered in this study. PLCs are highly influential in promoting informal teacher leadership, which in turn has a high positive linkage to teachers' focus on improving student learning. In addition, principal instructional leadership has a high positive influence on PLCs, while middle leadership has a moderate positive influence on PLCs. To further enhance teacher leadership capabilities that promote teachers' focus on improving student learning, we provide recommendations to boost PLC and middle leadership capacities in schools.