The purpose of this study was to elucidate the role and the implementation process of moral leadership in school improvement. Moral leadership appears to be an essential element for bringing about such improvements for two reasons. First, moral leadership, rather than a type or style of governance, represents the very essence of leadership, which is commonly present in various types of leadership. Secondly, the principles underlying moral leadership are in accord with those of a Professional Learning Community, an authentic and reliable model of school improvement. In order to examine the role and the implementation process of moral leadership in school improvement. the current study elucidated the principles of moral leadership through a systematic literature review and this constituted a theoretical framework for the present study. And this study performed a case study of two Catholic high schools and analysed the practical implementation process of moral leadership in the process of Catholic school improvement. Results of the case study suggested that the principals of these two schools played pivotal roles in the process of school change by putting the principles of moral leadership into practice, despite the fact that the leadership styles of these two individuals were different. Based on the current findings, the study delineated the implementation process of moral leadership toward school improvement, which is the following: the stage of initiation (the followership[commitment] of a leader /modelling a high standard of ethics / building the trust in relationship / establishing moral authority) → the first stage of implementation (building up the followership of the school’s faculty and staff / sharing values and vision) → the second stage of implementation (empowering the school’s teachers / building a culture of collaboration) →the stage of consolidation (consolidating self-motivation / building a Professional Learning Community).