As one of main theories of International Relations, Social Constructivism considers norms as the key elements of the identity building and forming the national interest of the states. This study has tried to apply the theory of constructivism to a comparative study of the Iranian and Saudi foreign policy toward the Middle East Peace plan from 1991 to 2004. The main question of the study regards the differences and the similarities of the two foreign policies and their reason. The main theorem of the study is: the Islamic Republic of Iran mainly opposed the Middle East Peace plan and the Saudi Arabia admitted that. The first looking after the Islamic values and the interest of the Islamic countries and the latter seeks its own national interests. Meanwhile the two have emphasized on the rights of the Palestinians and have supported Palestinian groups. With the division of the two different periods in foreign policy of the two countries before and after September 11 the following issues can be mentioned:

During 1991-2001, the foreign policy of the Iran concentrated on the absolute opposition to the plan and provoked the Palestinian resistance.

During 2001-2004, Iran followed more diplomatic language to show its opposition, while it encouraged other plans such as Amir Abdullah's.

During 1991-2001, the foreign policy of the Saudi Arabia encouraged the plan.

During 2001-2004, Saudi Arabia followed delicate support of the plan with some initiatives such as Amir Abdullah's plan.

Finally some guidelines have been presented to make Iranian foreign policy more efficient