To meet accountability demands, principals are being encouraged to enhance schools' organizational capacities by distributing leadership and initiating professional communities. Yet, relatively little attention has focused on how to develop the capabilities of potential co-leaders, and professional communities can be difficult to initiate and sustain. In this article, I examine how principals in three urban high schools fostered their department chairs' instructional leadership capabilities through professional communities. An interesting finding was the extent to which modeling, collaboration with peers, and skill-building activities enculturated department chairs into authentic communities of instructional leaders. The article concludes with implications for practice and research.