Iran’s nuclear dossier constitutes one of the most significant contemporary cases for analyzing the institutional mechanisms through which the independence of the International Atomic Energy Agency is constrained within the context of great-power competition. The main research question asks through which institutional pathways and at what levels the intervention of major powers is reproduced in the Agency’s decision-making processes, and how such intervention contributes to the securitization of Iran’s nuclear file. The research hypothesis holds that limitations on the Agency’s independence are not merely the result of episodic political pressure, but rather the outcome of a combination of structural features of the non-proliferation regime, bureaucratic reporting procedures, and dominant discursive patterns within the organization, which together enable the steering of technical assessments. The methodology is based on document analysis and qualitative meta-analysis of official IAEA reports, UN Security Council resolutions, and academic sources. Given the secondary and institutional nature of the data and limited access to informal decision-making processes, data triangulation across official documents, independent studies, and historical evidence is employed to enhance reliability. The findings indicate that major-power intervention operates at structural, bureaucratic, and soft levels, leading to the erosion of the Agency’s institutional autonomy and the political instrumentalization of its reports.