Previous research has been limited in examining the causal relationship between green transformational leadership (GTL) and green supply chain management (GSCM), with the intermediary influence of green human resource management (GHRM), within the pharmaceutical sector of the Kingdom of Saudi Arabia (KSA). This gap persisted despite the recognition in Saudi Vision 2030 of logistics, specifically, supply chain management (SCM), as fundamental to the national development agenda, given that contemporary competitiveness lies in the efficacy of supply chains (SCs) rather than individual companies. Moreover, the achievement of economic progress hinges significantly on how well these accomplishments align with sustainability demands and obstacles. This paper aims to investigate the extent to which GTL fosters GRHM practices to enhance the maturity of GSCM performance in the pharmaceutical industry in the KSA. In other words, the research goal is to explain the variance of GSCM due to GHRM and GTL. Drawing upon the Resource-Based View (RBV) and the Ability–Motivation–Opportunity theory (AMO), GTL can enhance many aspects of GHRM, such as employee performance measurement, training content design, recruitment criteria, and green-based rewards policies, which positively influence GSCM practices. The methodology employed is deductive and translated into a questionnaire derived from a comprehensive review of the existing literature. This questionnaire was subsequently tested through the collection of 111 responses from pharmaceutical companies operating in the KSA. The results show the critical effects of GTL and GHRM on GSCM in this sector. The research provides fresh theoretical perspectives and actionable recommendations based on the outcomes. As for originality, this research explores the contribution of transformational leadership and green human resource management in enhancing SC sustainability. The research provides directions for future research to investigate the mediating or moderating impacts of other significant factors, such as green thinking or eco-friendly behaviour, on SCM sustainability. As for practical implications, this research came up with an in-depth understanding of SC managers and professionals regarding their practices related to sustainability.