There are few options available for school managers who wish to effectively tackle school conflicts. The aim of the present work was to assess the issue of school conflict, its sources, and the effectiveness of different conflict management styles in Secondary Education school units in Greece. Teachers (n = 128) from twelve randomly selected schools in the region of Epirus, NW Greece, participated in the present work. Teachers' views on their school Principals' leadership style as well as the sources, the type(s), and the severity of conflict in their school unit were surveyed. Conflict appeared to be a frequent issue in schools. Frequent sources of conflict included interpersonal and organizational parameters. School leaders exhibited a range of conflict management styles. Compromise and Collaborative styles were frequently observed, followed by Smoothing and Forcing. Avoidance was less frequently exhibited by school leaders. The transformational and transactional leadership styles exhibited were equally effective in successful conflict resolution, whereas a laissez-faire leadership style was not. The results indicate that leadership and conflict management style can be associated with the effectiveness of conflict management.