Although the European Central Bank (ECB) is only an observer in the International Monetary Fund (IMF), its membership in the IMF will spark constitutional changes for both the EU and the IMF. The ECB's participation in IMF activities has so far been undertaken pragmatically, and is likely to evolve over time. This arrangement will limit the ECB's ability to fully develop in international monetary cooperation. This paper reviews what kinds of constitutional challenges the ECB faces in its bid for membership in the IMF. The research is based on the legal method and assesses the relevant provisions of both the EC Treaty and the IMF's Articles of Agreement. It also suggests some feasible approaches for ECB membership in the IMF.