Isolated teaching professionals run the risk of marginalization when schools undergo reform unless they have support for redefining and aligning their practice. The concept of Communities of Practice (CoPs) is demonstrated here to be a useful and powerful means for designing and supporting new roles and identities among education specialists. This chapter describes how a CoP developed when six isolated Teacher-Librarians joined university researchers in a project studying high schools undergoing reform. The description focuses on the specific activities that were utilized to encourage and support learning within the CoP. These attempts met with varying levels of success as the Teacher-Librarians began to reshape their professional identity and redefine their professional practice. The chapter explores the lessons learned in relation to the emergent and designed properties of a CoP striving to assist isolated practitioners working in educational contexts undergoing extensive change.