Green supply chain management (GSCM) practices are cross-organizational and closed-loop. They aim to reduce the ecological impact of the firm’s activity without sacrificing quality, cost, reliability, performance, or energy utilisation efficiency. This study presents empirical evidence to encourage firms to implement GSCM practices, which may enhance their competitive advantages. This study attempts to contribute to the growing research on GSCM practices—namelyinternal environmental management, green purchasing, eco-design and packaging, investment recovery, and cooperation with customers—and their effects on competitive advantages using a sample of 258 ISO 14001-certified manufacturing firms in Malaysia. A partial least squares structural equation modelling (PLS-SEM) analysis showed the direct effects of green purchasing, eco-design and packaging, investment recovery, and cooperation with customers directly on competitive advantages. However, internal environmental management did not relate to competitive advantages. Suggestions for future research are proposed. The study confirms the positive effects of GSCM practices on the competitive advantages of firms in the Malaysian manufacturing industry.