The objective of the study is to examine the mediating impact of competitive advantage on the relationship of supply chain management (SCM) practices and firm performance of the pharmaceutical industry of Thailand. For this purpose, the questionnaires were distributed among the 1400 supply chain manager which yield a 40% response rate. Based on SEM analysis, it is found that customer relationship (CR), time to market (TM), postponement (POS) have a significant association with the firm performance. While, supplier partnership (SP), information quality (IQ), information sharing (IS) have an insignificant association with the firm performance. On the other hand, it is found POS, CR, IQ, IS, SP have also a significant association with the competitive advantage, whereas, POS is not having a significant association with the competitive advantage. In addition, the mediating effect shows that competitive advantage has a partial mediating among all of the SCM practices and firm performance of the pharmaceutical industry of Thailand. These findings show that competitive advantage is considered to be a significant mediator in the relationship of relationship of SCM practices and firm performance of the pharmaceutical industry of Thailand. The current added a body of literature in the form of empirical findings which could become an area of interest for the future research. The research is also beneficial for the supply chain managers to know about the importance of SCM practices to improve the firm performance through the competitive advantage. The research limitations and future directions are also discussed at the end of the study.