Increased accountability measures over the past two decades caused schools to seek new ways to increase student achievement. As principals play a crucial role in implementing reforms to improve instructional practices and student achievement, understanding the competencies that make principals successful is essential. Research indicated that school principals may possess gaps in their knowledge of the change process, which can lead to the failure of school improvement initiatives. This study explored the connection between principals' knowledge of the change process and their self-efficacy as instructional leaders in a suburban Midwestern school district, hypothesizing that professional development in change leadership can enhance principals' self-efficacy for instructional leadership and likelihood to initiate change. Using a mixed-methods approach, the study utilized pre- and post-intervention surveys and qualitative interviews with seven head principals and five assistant principals from one school district. The findings revealed that professional development in change leadership positively influenced principals' self-efficacy for instructional leadership, as evidenced by quantitative analysis using the Norwegian Self-Efficacy for Instructional Leadership Scale (NSEILS) and qualitative interview data. The training enhanced principals' self-efficacy to set goals, provide feedback, and motivate teachers. Additionally, the training increased principals' confidence as change agents by providing a deeper understanding of the change process and effective strategies for implementing change. These results suggest that building leadership capacity for change management can significantly impact principals' self-efficacy and their willingness to initiate change, offering valuable insights for district administrators aiming to support school leaders in their roles as instructional leaders and change agents. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]