The Belt and Road Initiative (BRI) is at the threshold of a paradigm shift from a mercantilist approach to a comprehensive international development agenda. In this paper, we analyze the ideational roots of the "Green BRI" concept as one of the core elements of this strategic change. By applying a discursive institutionalist framework, we examine the impact of these ideological changes on China's domestic institutional framework governing the BRI. First, we provide a historical review of the mercantilist regime through decades of evolution of the Chinese international strategy, including the first decade of the BRI. We then examine the ideational mix around the "Green BRI" as part of the so-called BRI 2.0 discourse. We identified three embedded policy ideas: 1) to engage with the global governance system and development agenda; 2) to share Chinese development experience with the Global South, and 3) to address previous deficiencies manifested in the previous mercantilist era. These underpinning policy ideas are driving gradual but observable institutional changes within China, as new policy coalitions are emerging outside of the existing mercantilist regime, pressing the incumbents to consider more eco-friendly norms or practices. However, achieving a successful Green BRI requires profound institutional reforms. We also find that reducing the environmental footprints of Chinese overseas infrastructure projects can be challenging due to the persistent mercantilist beliefs and institutions, whereas promoting green industrial investments overseas can be relatively expedient given China's dominant technology and commercial capacities in the areas of renewable energy and electric vehicles.