Many Asia-Pacific countries still struggle to implement the procedural environmental rights—access to information, participation, and justice—outlined in Principle 10 of the Rio Declaration. To address this, a 2015 UN Human Rights Council report recommended that ASEAN adopt regional frameworks, specifically targeting environmental impact assessment principles. In alignment with this goal, the Advancing Environmental Rights in Asia and the Pacific project supports subregional legal frameworks to enshrine the right to a clean, healthy, and sustainable environment in South-East Asia as well as in the Pacific. This regional strategy ultimately drives crucial reforms in national policy, legislation, and judicial procedures. The project empowers Asia-Pacific stakeholders to accelerate environment-related SDGs by securing the right to a healthy environment through enhanced information access, public participation, and justice. Key milestones include adopting an ASEAN Leaders’ Declaration on Environmental Rights and securing a Pacific subregional strategy. Additionally, it establishes the Asia-Pacific Observatory on Environmental Rights to track progress and foster regional synergies. The overall performance of the project based on all the evaluation criteria was found to be highly satisfactory despite the challenges encountered during the early stage of the project. We conclude that the project has achieved its overarching objective to advance the development and implementation of subregional legal frameworks on environmental rights as a foundation to enshrine the right to a clean, healthy, and sustainable environment for all citizens at national level in South East Asia and the Pacific.