The proposed research undertakes a comparative analysis of the “peacebuilding” policies and practices of three major powers, Japan, the United States (US), and the European Union (EU), in Afghanistan since the fall of the Taliban government in late 2001. Peacebuilding, which has become a popular concept in international political discourse over the past decade, refers to the post-war reconstruction and development of conflict-affected countries, calling for a long-term commitment by international actors—beyond traditional and limited peacekeeping activities—to build sustainable indigenous capacities for improved conflict management in conflict-prone states and societies. Given that fragile states without properly functioning domestic institutions are prone to contribute to major international security problems, such as inter/intra-state conflicts, transnational terrorism, and Weapons of Mass Destruction (WMD) proliferation—and thanks also to the ongoing reconstruction and stabilization efforts in Afghanistan and Iraq—international peacebuilidng is viewed as one of the most pressing issues in world politics. The principle research questions to be addressed are three-fold: (1) What are the policies and approaches of Japan, the US, and the EU toward international peacebuilidng in general, and ongoing peacebuilidng efforts in Afghanistan, in particular?; (2) What kinds of coordination, both formal and informal, among the three donors—whether bilaterally between two of the three or possibly in a trilateral form—have been practiced in Afghanistan, and to what extent has such coordination contributed to the overall effectiveness of peacebuilding activities?; and (3) What is a desirable way to better coordinate overall assistance among major donors for Afghan peacebuilding, and how can this be achieved? As signified in these three sets of questions, this project engages a first-ever major systematic comparison of the policies and practices of these three key donors in Afghan peacebuilding. Given that many observers have already pointed out some conspicuous differences between the three actors in terms of their orientation towards peacebuilding assistance (e.g., emphasis on the security area, versus governance or development area), it seeks to delineate the key features of their activities and identify the sources of those characteristics. Further, the project sheds a particular light on the coordination and cooperation practices currently in place among the three actors. This focus reflects the fact that international peacebuilding, by its very nature, demands proper cooperation and coordination among donors, yet it stands as a most difficult area for such coordination in actual practice. Accordingly, it will critically examine the driving forces for their coordination arrangements and implications of these practices for the overall peacebuilding effort in Afghanistan. Drawing on these analyses, this project will elicit some concrete policy recommendations about ongoing Afghan peacebuilding activities, which now enters a critical phase in anticipation of a major reduction of foreign military forces deployed over the next few years. It will also make a meaningful contribution to the existing theoretical discussion in the study of international relations about the so-called “minilateral” approach for international cooperation and about the key determinants of foreign policy, while facilitating further discussion about the change and continuation of Japan’s foreign policy behavior.