Northeast Asia including China, Japan, Mongolia, Russia, DPRK and ROK, is a geographically close region that falls under the same environmental influence. Recently the region is not only facing serious domestic environmental problems with rapid economic growth, but also confronted with transboundary environmental problems and associated conflicts between countries. Unfortunately, Northeast Asia lacks a solid environmental management system among countries to deal with transboundary and other environmental issues. Transboundary Environmental Impact Assessment (TEIA) can, therefore, be one of the essential systematic measures in which environmental problems between countries would be negotiated. However, it would be necessary to have an indepth discussion of what we have to do first for implementing TEIA system in the region, and how to operate it while customizing each Northeast Asian country with different EIA system and socioeconomic circumstance. All these cannot be decided in a short time, and we need to invest enough time for discussing and considering them from various aspects. Recently, the Korean government declared "Eurasia Initiative". The initiative proposes important developing projects and ultimately plans to build a peaceful community throughout Eurasia based on comprehensive cooperation. The initiative aims to increase exchanges in transportation, energy and agricultural sectors to achieve the goals. In this regard, implementing TEIA in Northeast Asia is urgently needed and we have to prepare the strategy for introducing TEIA mechanism. Based on the results of 10 year experience on TEIA projects conducted since 2004, we suggest double-track approaches for developing TEIA mechanism. We continuously need to make an effort to establish a regional TEIA mechanism that all countries legally join, and simultaneously we also have to prepare a process to carry out TEIA for upcoming projects based on bi- or multi-lateral agreements. Practical solutions such as conducting pilot TEIA with relevant countries and developing TEIA guideline for the region could be the first step.