The rise of multinational corporations and the surge of foreign direct investment (FDI) have spread around the world. With the prevalence of FDI, many controversial investment cases have triggered national security concerns. This paper explores theoretical linkages between FDI and national security, while investigating political factors behind the U.S. foreign investment policy. This paper argues that due to consideration of national security and relative gains, a state is likely to conduct national security reviews toward foreign investments. By adopting a qualitative approach, this paper examines the case of U.S. FDI policy. The findings suggest that the U.S. FDI policy has been driven by political factors and gradually moved toward the direction of national security.