In response to the need for change in teaching practices, educators have bolstered efforts to provide professional development for teachers. However, research suggests that traditional models of professional development for educators are largely ineffective. Decades of research has also demonstrated that in order to bring about teacher change, teachers must have opportunities to engage in serious conversation with each other about practice, evidence, and alternatives. Teacher learning communities (TLC) are professional communities where teachers work collaboratively to reflect on their practice, examine evidence about the relationship between practice and student outcomes, and make changes that improve teaching and learning for their students. The current study focused on the role of 'teacher leader' in two of these professional learning communities over a one year period. The context for this study was a 3-year intervention designed to help teachers develop instructional strategies that support student motivation. This study examined how leaders facilitate reflective dialogue and collaboration, and how they respond to the obstacles posed by school culture. In addition this study examined how effective leadership facilitated understanding of student motivation. TLC meeting transcripts were analyzed using an open coding scheme to develop classifications for the dominant topics of discussion and modes of interaction in the group. Affiliation Network Analysis was also used to examine patterns of central group members, modes of interaction, and topics of discussion. The results suggest that teacher leaders can facilitate learning and collaboration in a group of their colleagues. However, in order for teacher leadership to be effective, teacher leaders must establish a norm of reflective dialogue as well as collaboration, and leaders must press and challenge their colleagues in order to establish this norm. Without it, teacher interaction and practice may not change. Results also suggest that the role of teacher leader may be a difficult one to take on as it requires a teacher to assume a position of leadership over colleagues. Conclusions have implications for aspects of teacher leadership that facilitate the formation of successful TLCs.