Iraq, as Iran's western neighbor, has the appropriate and potential capacity for regional interaction and cooperation. Accordingly, intelligent and planned interaction with this country can be important for the production of wealth, power and national security of Iran. Being aware of this, regional powers are also investing in Iraq ostensibly to rebuild the country, but in practice with political motives, and this could pose a threat to Iran. The present study seeks to answer the main question: What effect does the investment of regional powers in the reconstruction of post-ISIS Iraq, which is done in the shadow of the passivity of Iran's economic presence in this country, have on Iran's national security? The study claims that the investment of regional powers in Iraq, which leads to an increase in the influence of these powers and a change in Iraqi policies and orientations in the shadow of Iran's economic passivity in this country, increases Iran's national security threats in economic, political, social, military and environmental fields. The present study tries to investigate the subject with a descriptive-analytical method.