Seminal articles on organisational commitment in public organisations have assumed that employees reciprocate the attitudes of their peers, but recent studies suggest that the impact of managers' organisational commitment on employees' organisational commitment depends on how leaders convey their organisational commitment. In this study we investigate how transformational leadership moderates the relationship between mangers' and employees' organisational commitment. Multilevel data from surveys of 68 principals and 1,349 teachers in the area of upper secondary education show that there is no direct relationship between principals' and teachers' organisational commitment, but that transformational leadership moderates the relationship.