Turkish education system has enacted a vision of 2023 which emphasizes that school principals create and organize professional learning activities based on the needs of students and teachers. This research aimed to evaluate this vision by determining the level of support provided by school principals in teachers' professional development. It was based on a cross-sectional survey design of the quantitative method. The data collected from the 4,729 teachers working in Sanliurfa province in Turkey were analyzed. The results suggested that the school principals supported the professional development of the teachers occasionally and only 25.5% of principals supported teachers' professional development sufficiently. School principals mostly followed relevant resources to support teachers' professional development and inform teachers about innovations related to education. In addition, school principals did not adequately perform activities that may support teacher professional development such as determining individual and group development programs, organizing a professional development monitoring form for teachers, organizing educational activities outside the seminar period, receiving enough help from the experts in the area, and giving enough individual reading and research tasks. The results also indicated that the principals of high school teachers supported their professional development more than the principals working in primary and secondary schools, the principals of the classroom teachers and the principals of male teachers supported the professional development of the teachers more than the principals of the female and branch teachers and teachers' level of education did not create any difference in the perceptions of the teachers.