The purpose of the study is to research evaluation of the performance of environmental sustainability in automotive firms included in the BIST Sustainability 25 index and whether they comply with the disclosures contained in the firms' sustainability reports and environmental performance indicators in the GRI 300 series. The research has been done using the content analysis technique with data included in environment and climate change sections of the firms' sustainability reports. Thus, the sensitivity of firms in the automotive sector to environmental issues was tried to be determined based on their sustainability reports. In conclusion of the research, it was determined that the firms were very sensitive about environment and climate change and made satisfactory disclosures to their stakeholders. Regarding compliance with the GRI 300 Environmental Standards indicators, the study found that companies generally made sufficient disclosures on energy consumption, water and waste management, in spite of the fact that they did not make sufficient disclosures on biodiversity, environmental compliance and supplier environmental assessments.