This study aims to reveal the mediating role of teachers' moral courage (MC) behaviours in the relationship between school principals' authentic leadership (AL) behaviours and teachers' positive psychological capital (PPC) according to the views of teachers working in primary and secondary schools. In this study "AL Questionnaire", "PC Scale" and "PMC (Professional Moral Courage) Scale" were used. 8665 teachers working in primary and secondary schools in Antalya city centre comprise the population of this study. The sample of the study consists of 474 teachers reached by using the convenient sampling method. Confirmatory Factor Analysis (CFA) and (Cronbach Alpha Coefficient) alpha coefficients were benefited from the validity and reliability analysis of the scales, and Spearman's Correlation Coefficient, which was used for data that were not normally distributed, was used to determine the relationships between the variables, and structural equation modelling (SEM) was used for mediating analysis. A low-level positive and significant relationship was found between school principals' authentic leadership behaviours and teachers' psychological capital and moral courage behaviours. Following the results of the Structural equation modelling (SEM) analysis, it has been determined that the moral courage behaviours of the teachers have a mediating role in the relationship between the authentic leadership behaviours of the school principals and the positive psychological capital of the teachers.