Less is known about the professional development of experienced principals, defined here as having more than five years in the role, than that of aspirant principals. This deficit is somewhat surprising at a time when experienced principals are viewed as key players in two major international school leadership movements of the 21st century: the dramatically changing role of school leaders; and the rapidly expanding influence of globalization on the school leadership role. This study explored the professional development opportunities and needs of an experienced principal cohort in Australia. It utilized an iterative, three-phase, mixed method research design. Beginning with exploratory interviews, the study incorporated a broad state-wide survey followed by in-depth individual interviews. Cumulative analysis and triangulation of the data revealed the power of networking in experienced principals' professional development. This finding led to the identification of a significant leadership phenomenon particularly characteristic of this group: collective principal efficacy. The data revealed a need for networking to be recognized as a basis for building collective principal efficacy and to become a major professional learning strategy for experienced principals. The implications of these findings for the professional growth and well-being of principals, and for educational research, policy and practice, are discussed.