School leadership is a concept being discussed in recent studies regarding educational administration. This study examines the relationship between school leadership and teacher professionalism, focusing on the mediating effects of trust in the administrator on the relationship between school leadership and teacher professionalism. The study has adopted a cross-sectional survey design. The sample consists of 269 (Türkiye) and 134 (Turkish Republic of Northern Cyprus) teachers. The structural equation model was used to test the direct and indirect effects of the variables. Considering the findings of the study, school leadership is positively related to teacher professionalism as mediated by trust in the school administrator. In conclusion, the researchers recommend that school leaders implement practices that encourage powerful trust among teachers in their administrators.