This research examines the interaction between the Islamic Republic of Iran and the Iraqi Shia parties in the period from 2003 to 2021 and analyzes the role of these interactions in the formation and strengthening of the Shiite identity in Iraq with a constructivist approach. During this period, Iran has tried to counter the influence of other powers, especially Saudi Arabia, while consolidating its influence by providing military, economic and ideological support to Iraqi Shiite parties. to limit Iran's influence and change the balance of power in its favor. This competition between Iran and Saudi Arabia has led to the deepening of religious divisions in Iraq and divergence among the Shia parties, which itself has caused challenges in the political and security stability of Iraq. The research results show that Iran's interactions with Shiite parties have helped to strengthen religious identity and increase convergence between Iran and Iraq. But at the same time, the rivalry between Iran and Saudi Arabia has caused the spread of sectarian tensions and negative effects on the internal unity of Iraq. By presenting an analytical framework of the constructivist approach, this research comprehensively evaluates the dimensions and consequences of this competition and suggests solutions to improve regional interactions.. to limit Iran's influence and change the balance of power in its favor. This competition between Iran and Saudi Arabia has led to the deepening of religious divisions in Iraq and divergence stability of Iraq. The research results show that Iran's interactions with Shiite parties have helped to strengthen religious identity and increase convergence between Iran and Iraq. But at the same time, the rivalry between Iran and Saudi Arabia has caused the spread of sectarian tensions and negative effects on the internal unity of Iraq. By presenting an analytical framework of the constructivist approach, this research comprehensively evaluates the dimensions and consequences of this competition and suggests solutiamong the Shia parties, which itself has caused challenges in the political and security stability of Iraq.