"Teacher leadership" is often described as a murky concept that refers not to a particular position, but rather to varied formal and informal leadership roles that teachers play within school communities. Teacher leadership may involve shaping curricula, choosing instructional materials, leading professional book clubs, planning staff development, serving as instructional coaches, or involvement in a host of other activities. This article examines the nature of teacher leadership as nurtured through long-term professional development; provides an overview of the Master Teacher Program, a 3-year program aimed at nurturing teacher leaders; and offers concluding evidence of the ways in which professional development has the potential to support teacher leadership among early childhood educators.