Background and objective: This article examines the evolution of the Republic of Korea’s environmental diplomacy toward ASEAN from 2008 to 2025, focusing on the development of cooperation on green and circular economies.Methods: Using a historical-institutionalist perspective and the analytical lens of environmental diplomacy, the study investigates how successive administrations transformed green growth from a strategic policy vision into concrete programs for sustainable development in Southeast Asia. The analysis integrates historical comparison, qualitative policy assessment, and discourse analysis of major strategies, institutional frameworks, and cooperation initiatives.Results: The findings reveal a shift from the normative and declaratory orientation of the Lee Myung-bak and Park Geun-hye governments toward more institutionalized and technology-centered cooperation under Moon Jae-in and Yoon Seok-yeol. Through initiatives such as the Green New Deal, the New Southern Policy, and emerging Korea-ASEAN green and circular economy platforms, the Republic of Korea expanded its engagement by supporting renewable energy development, waste management, and circular production systems. As a result, Korea’s environmental diplomacy has evolved into a multidimensional framework that combines technological assistance, financial support, and capacity building to facilitate ASEAN’s low-carbon transition and broader sustainability goals.Conclusion: Situated within the broader regional and historical context of East Asia, the study demonstrates that environmental cooperation functions not only as a developmental instrument but also as a source of soft power and regional legitimacy for a middle power seeking to contribute to ecological security and sustainable development.
Phan Thi Anh Thu (Sat,) studied this question.