The concept of environmental sustainability, which is becoming increasingly important today, the determination and weighting of its criteria, the evaluation of the performance of the enterprises constitute the Multi-Criteria Decision Making (MCDM) problem. In this study, the three-year environmental sustainability performance data on the Zorlu Energy group's website were weighted with the Entropy method, one of the MCDM methods, and ranked with the CoCoSo (Combined Reconciliation Solution) method used in ranking and selection methods. The criteria that are effective in environmental sustainability performance are listed in order of importance. In the calculation, the 'energy consumption' criterion was calculated as the highest weighted criterion. In 2019, Zorlu Energy's environmental sustainability performance was the highest, while 2018 was the lowest.