School personnel across the United States are developing additional teacher leadership roles to improve professional learning and retain effective teachers. More information is needed concerning how middle school principals are guiding the development of teacher leaders in their schools. The purpose of this qualitative case study was to explore the leadership strategies used by middle school principals to develop and support teacher leaders in their schools. Bass's conceptual framework of transformational leadership guided this research. Research questions were designed to explore how middle school principals in urban schools understood their roles in teacher leader development and the leadership strategies employed to guide the development of teacher leaders in their schools. Eight middle school principals from one urban district in the northeastern United States participated in semi structured interviews and provided archival documents from teacher leader training agendas and team meetings minutes. Participants had a minimum of 3 years' experience at their schools. Thematic analysis employing a priori, and open coding were used to analyze the data. Findings indicated that middle school principals used two approaches to guide and train the development of teacher leaders: (a) fostering a culture of leadership development that included collaboration and trust and (b) building the capacity of principals and teacher leaders by providing leadership tasks and experiences. Future research could expand the scope of the study to include the perspective of teacher leaders. Positive social change implications include improving urban middle schools by helping principals understand the need to develop and support teacher leaders, to enhance the retention of teachers, and to increase the professional community's effectiveness. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]