The present research aims at examining the role of United Against Nuclear Iran (UANI) organization, which is known as a political thin tank and lobby in the U.S. foreign policy. Think tanks and political lobbies, as informal actors, have influenced the U.S. foreign policy since their emergence. UANI have focused on Iran’s nuclear program. The think tank established by former U.S. ambassador to the UN during Bush’s tenure, Mark Wallace, the U.S. special envoy to Afghanistan and the U.S. ambassador to the UN during Clinton’s tenure, Richard Holbrooke, former CIA director, Jim Woolsey, and expert on Middle East, Dennis Ross, has launched various domestic and international activities against Iran. This research seeks to answer the following question using system theory in decision-making theory: What are UANI’s tools for influencing the U.S. foreign policy and what is its role in the U.S. foreign policy towards Iran’s nuclear program? Connection with the main power centers and formal actors in the U.S. foreign policy decision-making process, interaction with high-ranking officials in the U.S. foreign policy realm, and relationship with main lobbies in the U.S., are some of UANI’s activities that demonstrate its active role in the U.S. foreign policy.