In several contexts, reform in the training and nomination of future school principals was based on competency profiles. In Québec, it was not until 2008 that its Ministry of Education established a profile of competencies specifically for school principals. This study proposed a questionnaire on the perceptions and self-efficacy beliefs of school principals with regard to these competencies and their associated factors. Respondents gave greater weight to the management of education services, followed by human resources, educational environment, and finally, administration. A significant difference was observed between administrative management and the teaching level and school size. The principals whose professional development activities consisted of conventions and seminars also felt a greater sense of personal efficacy on this factor compared to the principals whose professional development was done through mentoring.