The concept of professional learning communities (PLCs) has attracted global attention because of its significant role in facilitating teacher professional learning. While increasing efforts have been invested in building PLCs in many systems, few studies have investigated how teacher leaders lead and sustain PLCs. Drawing on qualitative findings from a Shanghai secondary school, this paper explores the role of teacher leaders in formal positions and their leadership practices in promoting teacher professional learning in PLCs in China. The analysis reveals that formally appointed teacher leaders are recognised based on their professional expertise, and they exercise strong professional-oriented leadership practices facilitating the subject-based PLC process. Further, positional and professional authority in teacher leadership are not mutually exclusive in the Chinese school context. The study argues that teacher leadership development has great potential for sustaining productive PLCs in the school setting.