Transparency is now a core principle in environmental and resource governance. Responding to calls for a clearer identification of pathways from transparency to effective change, this article identifies three “Theories of Change” for governance-by-disclosure and applies them to the Extractive Industries Transparency Initiative (EITI). Among the best known global transparency initiatives, the EITI has used an inclusive multistakeholder governance model and elaborate compliance standards, disclosing trillions of dollars in natural resource revenues. Yet, after two decades, the EITI is still largely without an explicit and proven theory. This study finds that a Theory of Change for the EITI is possible, valuable, and even necessary as the EITI risks becoming obsolete in some participating countries. The proposed Theories of Change provide valuable templates for environmental and resource governance, yet such models need to reflect national contexts, needs, challenges, and objectives to ensure fit and effective implementation, including measures enforcing accountability.