© 2020 Informa UK Limited, trading as Taylor & Francis Group. This article provides empirical evidence of the emergence of new private governance forms through three case studies: transboundary air pollution, green supply chain, and energy transition in Northeast Asia. This article also refers to private governance theories discussed in the context of global environmental governance. Consistent with the private authority theory, entrepreneurs with vast expertise and capacity to provide useful information and practices have emerged. They allow stakeholders to cooperate in regional environmental sustainability under the conditions of weak or no focal institutions and heterogeneous state preferences. This observation is consistent with the global trend of environmental governance, which is shifting from regulatory-based to goal-setting governance. As global partnership theory suggests, hybrid forms of private governance, including various local- to global-level public–private partnerships, emerge across the cases. However, these forms of governance are still in the embryonic stage, where their functions of private authority are not fully developed. These insights challenge the predominant view on the limited roles of nonstate actors in building regional environmental governance in Northeast Asia as discussed in the existing literature.