This study investigates and analyses the practice of reporting ESG (Environmental, Social, and Governance) within the plastic industry supply chain at PT. MSI, as well as the function of sustainability reports in corporate governance. It was due to the stakeholder’s intense pressure and environmental awareness regarding the plastic industry. Therefore, ESG reporting became a strategic issue which was unavoidable for the company. The study applies qualitatively with a descriptive approach. Furthermore, the population consists of plastic industry manufacturing. The data were gathered through deep-interviews with key informants who were directly involved in the planning and implementation of ESG reporting, as well as observation, and company’s document analysis of the company’s sustainability report. Moreover, the data were analysed using descriptive-qualitative analysis which incorporated empirical findings in legitimation, stakeholder theories, Green washing and transparency issues. As a result, it shows how practice of ESG reporting at PT. MSI evolves continually in response to external pressure, especially global and regulator customers. Meanwhile, sustainability report serves not only as an external legitimation tool, but also as an internal control mechanism that promote governance restoration, documentation discipline, and cross functionality. Despite the limitation of data harmonization and sustainable accounting integration, ESG reporting at PT. MSI shows shift from a symbolic approach to a more meaningful practice focused on long-term sustainability.