To study on U.S.-Malaysian relations after September 11, 2001. Employing the concept of interdependence as a framework of analysis factors affecting the U.S. and Malaysia relations after September 11, 2001. The hypothesis of this thesis is that diplomatic normalization and close relations between these two countries after September 11, 2001, was determined by their respective economic and security interests in the context of a changing international situation from “war on terrorism”. According to the study, the U.S. counter-terrorism policy toward Southeast Asia after September 11, 2001, have deeply effected on close relationship on economic and security cooperation. In economic relations, the U.S. and Malaysia signed a free trade agreement (FTA). Actually, both countries have continually cooperated on economic since Mahathir’s liberalism policy. Therefore, September 11, 2001 have accelerated their closer relations. Although they have a connection increasingly on security, Malaysia has to concern about public opinion and Muslim world attitude. For example, Malaysia is against the U.S. conducting any sort of military-like operation in the country.