The purpose of this study was to investigate the managerial leadership styles of school principals for school effectiveness at secondary schools of the Dutywa Education District in the Eastern Cape Province of the Republic of South. The literature review reflects theories concerning the managerial leadership styles of school principals for school effectiveness. In order to attain the aims and objectives of the study, the researcher used the qualitative research method, both in collecting and analyzing the data. The case study design was used to describe and access the phenomenon and the purposive sampling method was used to select (6) secondary school principals. An open ended interview schedule was used for the face-to-face in-depth interviews on the managerial leadership styles of school principals for school effectiveness at secondary schools of the Dutywa Education District. Themes were drawn from the responses of the participants and analysed. Some of the findings were: Democratic and participatory leadership styles were used by the school principals to achieve maximum co-operation from both experienced and beginning teachers and the learners in the schools. Laissez fair and autocratic styles of leadership appeared to be undesirable for the management of schools. For school principals’ effective management, they need to do proper planning, organising and scheduling of activities, assigning duties to teachers and delegating some of their work to competent teachers. The reasons for school principals’ ineffectiveness in this study were: favouritism, over-familiar relationships with some teachers, ignoring teachers’ personal problems, workload, lack of support and co-operation from teachers. Incorrect interpretation of educational policies were seen to lead to chaotic situations, poor performance of both teachers and learners, division between learners and teachers, a lack of unity between school stake-holders, poor job satisfaction and lack of trust and respect for the principals concerned. Factors contributing to principals’ incorrect interpretation of educational policies and execution of management roles were: negligence, lack of knowledge and ability to interpret educational policies, lack of proper induction programmes and training of principals and lack of support on policy matters from the Department of Education. Contributing factors resulting in barriers to principals’ ineffectiveness in the management of schools were: failure to give proper instructions to teachers and learners, failure to effectively use of available funds in the school, failure to implement all educational programmes in the school including co-curricular and extra mural activities, lack of experience, lack of support from both the Department of Education and the parents, lack of resources, high staff turnover, favourtisms and failure to hold teachers accountable for poor work done. Mechanisms deemed to overcome the factors leading to barriers to principals’ execution of their management roles at schools were: making the effort to be knowledgeable about educational policies, timely responses to problems in the school, regular consultation with stakeholders, employment of SGB teachers, taking direct supervision of instructions in classrooms and endeavoring to have good relations and gaining support from the SGB and the parents. The researcher made some recommendations on the managerial leadership styles of school principals for school effectiveness at secondary schools of the Dutywa Education District.