Perhaps one of the most important characteristics of the new Iraq is the influence of a wide spectrum of domestic groups, regional actors and extra-regional powers on its political- security and economic developments. Regardless of the role played by political and economic structural factors, historical background and different Iraqi groups, among other regional and extra- regional powers, Iran and the U.S. play a prominent role in state- nation building in Iraq. It seems that every plan for establishing peace in the new Iraq which is in conflict with Iran's national security will face serious challenges. In the past three decades, Iran and the U.S. each have tried to eliminate the other one. However, the continuation of instability and insecurity in Iraq as well as existing concerns about the escalation of Iraq's crisis to a regional conflict led to the revision of the U.S. unilateral policies and its efforts to leave aside Iran from regional equations. This article studies some dimensions of policies, interests and actions pursued by Iran and the U.S. in Iraq. Then, the author explores their commonalities regarding the restoration of peace and stability in Iraq.