China's Belt and Road Initiative (BRI) has attracted much attention in the field of transportation research. With a primary goal to improve regional and global connectivity, the initiative proposes a massive development programme of transportation infrastructure (TI) linking China with the rest of the world. While it creates a tremendous development opportunity, the unprecedented scale of TI construction also brings various challenges. In particular, the environmental impacts of the TI projects are of critical concern. Herein, smooth implementation of the TI projects would depend on the capacity of all the concerned actors to conduct collaborative planning and integrate environmental considerations. Therefore, from a multi-actor perspective, this paper aims to provide a unified framework of the environmental governance of the TI projects under the BRI. The goal is achieved through a focused review of relevant research articles and technical reports published in both English and Chinese. Based on the review findings, the framework along with four propositions are derived, focusing on the key actors (who), the environmental considerations (what) and the governance structures (how). The study concludes with theoretical and managerial implications.