Voluntary standards certifying environmental qualities of labeled products have proliferated across sectors and countries. Effectuating these standards requires the collaboration among and between creators (typically firms and nongovernmental organizations) and adopters (firms across a particular supply chain). However, the need to collaborate does not rule out the presence of controversy. Drawing on the case of the Marine Stewardship Council, a leading seafood standard to conserve the world’s threatened marine fauna, we analyze how this controversy, from economic and sociologic vantage points, impacts a sustainability transition. In essence, interest divergence drives controversy over standard design, which spurs controversy over standard effectiveness and prompts the proliferation of competing standards. Controversy is magnified by the opacity or nontransparency of the fields which such standards seek to govern. We conclude that, while interest divergence and field opacity entail inherent controversy over voluntary environmental standards, the impact of this controversy on sustainability transitions is typically predominantly positive.