This chapter explores effective turnaround leadership practices as perceived and implemented by school principals in Cambodian upper secondary schools, particularly in underserved and low-performing regions. Employing a phenomenological methodology, the study draws on semi-structured interviews with 21 school leaders recognized for their leadership effectiveness. The findings reveal a multifaceted model of turnaround leadership that emphasizes visionary guidance, data-driven decision-making, professional ethics, inclusive and distributed leadership, community engagement, and resilience. Furthermore, the study identifies internal and external factors shaping leadership practices, including training, resource allocation, technology access, teacher capacity, and policy support. Despite significant contextual challenges, Cambodian school leaders have developed innovative and culturally grounded approaches to improve student outcomes and institutional performance. The study contributes to the global discourse on school improvement by offering insights from a developing country perspective, where the interplay of traditional values, systemic constraints, and leadership innovation shapes educational transformation. Implications are provided for policymakers and practitioners aiming to strengthen leadership capacities in similar contexts.