Recently, there has been more focus on issues related to the professional development of teacher leaders (TLs), but there is still much to learn. Situated within a larger study, the purpose of this research was to understand the ways in which individuals participated in teacher leadership and how participation and identities shaped and were shaped by communities of practice (Lave & Wenger, 1991). Specifically, this study focuses on two TLs and the manifestation of what we are describing as 'thick' and 'thin' TL identities. Based on our findings, we see thick identity--that is, a TL identity that is deeply rooted in who the person is--as possibly more desirable than a thin TL identity, or a TL identity in which one might see themselves occasionally as a TL when they are called on to lead. This has implications for the theorizing of and professional development for teacher leadership.