Over the past three decades, the establishment of partnerships between public and non-state actors has become a leading mechanism of inter-organizational collaboration for sustainable development. The presence of productive collaboration inside a partnership, as well as a partnership’s ability to influence collaboration and institutions outside the immediate partners, are usually considered important pathways to partnership effectiveness. The conditions which facilitate or undermine such collaboration, however, are still widely debated. In this article, we draw on the literature on institutional and partnerships effectiveness to explore how the institutional design of a partnership, and more specifically the quality of its contractual arrangements, may influence the ability of the partners to come together, articulate partnership goals, gain access to additional sources of financing, and manage reputational risks and gains. We do so through a case study of the Galápagos San Cristóbal Wind Project partnership, which was established in 2003 to reduce the Galápagos Islands’ dependence on imported fossil fuels, while simultaneously protecting the region’s fragile marine ecosystem from the risk of oil spills and contributing toward the transition to cleaner energy sources. Overall, we find that the high quality of contracting used in the partnership, including the supporting role of domestic legislation, was instrumental in shaping the effectiveness of the project activities and also served as a catalyst to facilitate adaptability and the credible commitment of resources by the partners. While we note the importance of considering contextual factors and conditions before applying our findings to other types of more informal collaborative relationships, we argue that the theoretical focus on contractual arrangements emphasized in our article is likely to remain important for understanding the effectiveness of global partnerships for sustainable development.