Conflict between transnational environmental issues and foreign investment in capital-importing states can be commonly found. Actually, several investor-state dispute arbitration cases like Bilcon v. Canada, S.D. Myers v. Canada, and Metalclad v. Mexico concerned environmental matters. States are worried about their measures for securing the environment might be deemed to go against international investment agreements and foreign investors also are anxious because of excessive regulations. Against this backdrop, stakeholders attempt to strike a balance between securing foreign investment and preserving the environment. This article argues that the investment chapter of the Korea-US FTA tries to solve environment-investment collision in investor-state disputes. Before analyzing the provisions of the investment chapter most relevant to environmental issues, this article points out the most typical types of environmental clauses included in international investment agreements. The investment chapter of the Korea-US FTA has provisions which effectively prevent measures from becoming useless when those measures are legitimate measures relevant to environmental matters. This does not mean that the Korea-US FTA completely solves the conflict between environmental issues and the protection of foreign investment, but still it paves the way for a prudent solution which would hash out this thorny problem.