This study examines the decision-making process of the Greater Middle East Project (GMEP) from the perspective of cognitive biases and behavioral decision-making psychology within a normative-analytical comparative framework. The primary objective is to explain which cognitive mechanisms shaped the decision logic of GMEP and why it systematically deviated from normative rationality assumptions. The study adopts a qualitative research approach and single-case analysis method, employing conceptual analysis, comparative theoretical evaluation, and document review based on secondary sources. Research findings reveal that confirmation bias, overconfidence bias, framing effect, and planning fallacy exhibited realization levels ranging from approximately seventy to eighty percent in the decision-making process. These biases were found to operate not independently but within a cyclical interaction network that mutually reinforces one another. The study demonstrates that cognitive biases are reinforced not only at the individual level but also within institutional decision making structures, with groupthink dynamics and epistemic communities playing mediating roles in this reinforcement process. The profound gap between normative discourse and analytical outcomes is conceptualized as the product of cognitive distortions. The research makes an original contribution to the behavioral international relations literature by demonstrating that foreign policy failures can be explained through structural cognitive dynamics rather than individual shortcomings. The theoretical contribution lies in integrating normative and behavioral approaches within a comparative framework, while the practical contribution consists of developing concrete recommendations for integrating cognitive correction mechanisms into policy design.