This research explored the relationship of principal leadership and teacher professional learning in China and Thailand. The authors tested a conceptual model in which teacher trust and agency were proposed as mediators of the effects of the principal's learning-centered leadership on teacher professional learning. Common survey measures had been used to collect data from 1259 teachers in 38 schools in mainland China and 1071 teachers in 60 schools in Thailand. Multi-group confirmatory factor analysis, multi-group structural equation modelling, and bootstrapping were employed to compare the proposed leadership and teacher learning processes in Chinese and Thai schools. The results confirmed a similar model of strong, statistically significant, 'mediated effects' of principal leadership on the professional learning of teachers in the two societies. These findings contribute to our understanding of leadership effects across societies and offer insight into how policymakers and practitioners can support school leadership, teacher development, and educational change.