This study focuses on essential competencies for principal turnaround leadership in low-performing Vietnamese schools, particularly in ethnic minority regions. A qualitative single case study was conducted at a high school in Yen Bai province, where substantial improvements were achieved under an experienced principal’s leadership. Data were collected through semi-structured interviews with the principal and 15 teachers, along with document analysis of improvement plans and academic records. Six key competencies emerged as critical to turnaround success: strategic vision-building, cultural-contextual intelligence, resource mobilisation, democratic leadership, strategic vision implementation, and resilient adaptability. These competencies enabled principals to navigate resource constraints, cultural diversity, and centralised governance, driving meaningful school transformation. Principals demonstrated the ability to align national education policies with local needs, fostering collaboration and trust by blending Confucian values with ethnic traditions.