This work emerged from funded research examining collaboration among stake-holder organizations present at three U.S. nuclear weapons complex sites. The authors examine issues such as how and why stakeholder groups form collaborative alliances when dealing with the target organization, what leaders of stakeholder organizations actually think about when collaborating to deal with the target organization, and what outcomes result from the collaboration process. Drawing on stakeholder theory and research in interorganizational collaboration, the authors used an inductive, interview-based methodology to build a model of collaboration among nonprofit stakeholder groups. The model contributes to the descriptive stream of stakeholder theory and, in turn, has implications for the instrumental stream. The model also offers implications for future researchers, leaders of stakeholder alliances, and leaders of target organizations.