This descriptive-correlational study examined the influence of school leadership support on teachers’ use of PISA-like assessments in public secondary schools in Diffun District during the 2025-2026 academic year. It includes 70 Grade 9 and Grade 10 teachers in English, Mathematics, and Science selected through stratified sampling. It aimed to measure teachers’ profiles, perceptions of leadership support, and frequency of use of PISA-like assessments. The data were analyzed using frequency, percentage, median, Mann-Whitney U test, Kruskal-Wallis test, and Spearman’s rank correlation. Findings revealed that teachers perceived a high level of leadership support, particularly in vision, monitoring, and feedback. Teachers also reported a very high frequency of integrating PISA-like assessments, including higher-order thinking skills and real-world tasks. No significant differences were found across sex and the subject taught, although Grade 10 teachers reported better access to resources. A significant positive relationship was established between leadership support and teachers’ frequency of use of PISA-like assessments. This study concludes that strong institutional support enhances the consistent implementation of PISA-aligned assessment practices in public secondary schools.