Background: Indonesia's palm oil industry faces growing sustainability pressure, including compliance with the European Union Deforestation Regulation (EUDR). Following its December 2023 merger, PT Perkebunan Nusantara IV PalmCo is integrating ESG principles into its operations. Objective: This study aims to analyze the implementation of circular economy and carbon emission reduction strategies as part of the ESG framework at PTPN IV PalmCo. Methods: Using a descriptive qualitative case study with secondary data from company reports, verified media, and official documents (2023–2025), this research finds that PalmCo has implemented a circular economy by converting palm oil waste into renewable energy through 11 biogas facilities, targeting 32 facilities by 2029 and over 80% renewable energy utilization. Results: The carbon emission reduction strategy, implemented through both nature-based and technology-based approaches, has resulted in carbon sequestration of 873,395 tons CO₂e/year and emission reductions of 191,107 tons CO₂e/year, while also achieving the first Greenhouse Gas (GHG) Emission Reduction Certificate in the plantation industry. Both initiatives are strongly integrated into the ESG framework, as evidenced by PalmCo’s #2 global ranking in the S&P Corporate Sustainability Assessment (CSA) 2024 and its receipt of two Diamond Awards at the ESG Initiative Awards 2025. Conclusion: This research contributes to ESG literature in the plantation sector by demonstrating, through Legitimacy Theory, that PalmCo is transitioning from symbolic to substantive legitimacy, evidenced by verified emission reductions and the integration of ESG indicators into management KPIs. These findings offer a theoretical contribution to ESG implementation in state-owned plantation enterprises.