Trans-boundary environmental impact assessment (TEIA) applies to the relationship between States, with provisions found in customary and treaty law; it may also apply within a State, where there are separate jurisdictions. This article considers both of these dimensions from the experience of the Greater Tumen Initiative in Northeast Asia, and in the Pearl River Delta Region in South China. The fact that both areas focus on river basins is significant, as much experience with TEIA relates to trans-boundary rivers. TEIA is defined with reference to the Convention on Environmental Impact Assessment (EIA) in a Trans-boundary Context (the Espoo Convention). Recommendations include a more widespread application of TEIA, establishment of new governance structures and amendment of China’s domestic EIA Law.