Population is one of the key factors influencing security. An increase or decrease in population can lead to security challenges such as unemployment, resource shortages, urban congestion and a decline in education and healthcare standards. Additionally, changes in age structure, density and population distribution impact social and economic relations. this article aims to examine the effects of demographic changes on security dynamics between Iran and Iraq through a comparative case study. The research question posed is How do demographic changes influence security dynamics between Iran and Iraq? In response, the research hypothesis suggests that demographic changes serve both as a factor for interaction and cooperation and as a factor for conflict and competition between the two countries. If demographic changes lead to imbalances in population, urbanization, age, gender, and migration, security tensions will escalate. Conversely, if demographic changes align with economic, political and social development, they will pave the way for mutual cooperation and enhanced security in both countries. the research method is qualitative, employing the analysis of quantitative data. Based on an evaluation of existing sources, the method of data collection has been determined as library research. the findings indicate that demographic trends in these two countries differ significantly and have various effects on their internal and external stability. Accordingly, it is suggested that fostering cooperation between Iran and Iraq should be prioritized to enhance security and promote economic, political and social development, leveraging demographic changes as a positive factor for growth and progress