This research aims to investigate the effects of leadership behaviour of school principals on teachers' organisational commitment in Turkey. The method of meta-analysis is used to calculate the effects size of leadership on teachers' organisational commitment. Besides this, leadership style, publication type and publication year are used as moderators in order to explain variation in effect sizes. The analysis results of the random effect model showed that leadership has a very strong and positive effect on teachers' organisational commitment. Particularly, supporting, democratic and transformational leadership styles affect organisational commitment of teachers more than other leadership approaches. However, except leadership styles, the other moderators chosen for the research are not a powerful determinant of the relationship between school leadership and organisational commitment.