<![CDATA[Although collaborative leadership and Professional Learning Communities (PLCs) have been widely discussed in teacher professional development, limited understanding remains regarding how teachers enact collaborative leadership through PLCs to enhance professional performance, particularly in Islamic secondary schools. This study aims to examine teachers’ collaborative leadership practices, the implementation of PLCs as platforms for professional learning, and the role of collaborative leadership through PLCs in improving teachers’ professional performance. This study employed a qualitative case study design at SMA IT Dhiaul Fikri, involving 24 participants comprising school leaders, teachers, and students selected through purposive sampling. Data were collected through in-depth interviews, participant observation, and document analysis and were analyzed using an interactive model consisting of data condensation, data display, conclusion drawing, and verification. The findings reveal that collaborative leadership is manifested through teacher participation in academic decision-making, collaborative reflection, mentoring, and the distribution of responsibilities based on professional expertise. PLCs function as structured platforms for collective professional learning through instructional discussions, knowledge sharing, reflective dialogue, and collaborative problem-solving. The findings further indicate that PLC practices mediate the relationship between collaborative leadership and professional performance by improving instructional planning, classroom implementation, reflective practice, pedagogical competence, and instructional innovation. This study concludes that collaborative leadership enacted through PLCs promotes sustainable professional learning and enhances educational quality in Islamic secondary school contexts. Its contribution lies in extending the literature on distributed leadership and PLCs while offering practical insights for strengthening collaborative school cultures and teacher professional development. Future research should examine these relationships across diverse educational contexts using comparative and longitudinal designs. Keywords: Collaborative Leadership; Professional Learning Community; Teacher Professional Performance; Teacher Professional Development; Distributed Leadership]]>
