Corporate social responsibility (CSR) scholarship has recently taken a “political turn” in its study of how firms are increasingly involved in providing public goods and shaping business regulation. In this paper, we focus on multi-stakeholder initiatives (MSIs) as one way of achieving collective company self-regulation. We conjecture that once with the number of MSI members rising, an increasing heterogeneity of interests may create tensions between “deepening” and “enlarging” the initiative’s activities. These tensions can become self-reinforcing, resulting in dilution of the original mission. Based on nine conceptually derived propositions, we develop a process model that illustrates the “paradox of success,” which is when the very success of an MSI may lead to abuse, deadlock, or loss of legitimacy. To overcome these challenges, we make five suggestions for management, addressing communication, governance, and mission focus. We use the Extractive Industries Transparency Initiative to illustrate our arguments.