The purpose of this study is to examine the effect of green supply chain management on firm performance with competitive advantage as a mediator. This study used purposive sampling to obtain a population comprising 516 companies which were part of a program called PROPER (which stands for Program Penilaian Peringkat Kinerja Perusahaan or company performance rating program) between 2010 and 2018. The data were obtained from the Indonesia Stock Exchange and OSIRIS software and were tested using STATA. The results obtained in this study demonstrate that green supply chain management has a positive effect on competitive advantage, competitive advantage has a positive effect on firm performance, and green supply chain management has no effect on firm performance. Competitive advantage is able to mediate the relationship between green supply chain management and firm performance. The results of this study provide insight into the importance of implementing green supply chain management in order to be able to create a competitive advantage and improve firm performance in the midst of intense competition.