This study examined the relationship between the transformational leadership of Thai school administrators and the teaching performance of Filipino teachers in selected schools in Nonthaburi, Thailand. A quantitative descriptive-correlational research design was employed. The respondents consisted of 156 Filipino teachers selected through simple random sampling. Data were collected using adapted and validated survey questionnaires measuring the transformational leadership practices of Thai administrators and the teaching performance of Filipino teachers. Ethical protocols were strictly observed throughout the data collection process. The data were analyzed using descriptive statistics (mean), Pearson's product-moment correlation coefficient (Pearson's r), and multiple linear regression. The findings revealed that the transformational leadership of Thai administrators was rated as very highly extensive, indicating that transformational leadership practices were consistently demonstrated. Likewise, the teaching performance of Filipino teachers was assessed as extremely effective, suggesting consistently high levels of teaching performance. Pearson's correlation analysis indicated a strong, positive, and statistically significant relationship between the transformational leadership of Thai administrators and the teaching performance of Filipino teachers. Furthermore, multiple linear regression analysis identified Model the Way as the transformational leadership dimension that significantly predicted the teaching performance of Filipino teachers. The findings underscore the critical role of transformational leadership in enhancing teachers' instructional performance. Strengthening transformational leadership competencies among school administrators may contribute to improved teaching effectiveness. Consequently, educational policymakers, school leaders, and program planners are encouraged to develop and implement leadership development initiatives that cultivate transformational leadership practices to foster sustained improvements in teacher performance. Keywords: transformational leadership, Thai school administrators, teaching performance, Filipino teachers, descriptive-correlational study