Knowledge management systems in enterprises have the ability to support the exploitation, integration, and transfer of knowledge, allowing the components of the system to reallocate knowledge for better use. An effective knowledge management system can improve the ability to access, deploy, and develop knowledge for enterprises to enhance decision-making, learning, and innovation capabilities. There are very few studies addressing the impact of knowledge management system quality on competitive advantage, and no studies have been conducted in the context of small and medium-sized enterprises in Vietnam. This article conducts research to identify and explain the above problem. The results demonstrate that knowledge management systems play an important role in creating and maintaining competitive advantage.