In the past decade, many healthcare institutions have formed new partnerships, alliances, and networks. Collaboration among chief nursing officers and other leaders from affiliating institutions is essential to the success of these new organizational structures. The authors explore the nature of the collaboration among chief nursing officers and senior nurse leaders at 5 Harvard-affiliated teaching hospitals that provide cancer care. In particular, this article examines how collaborative relationships have been fostered and highlights the challenges, benefits, and outcomes of successful cross-institutional collaboration.