Following the adoption of the Magnitsky Act in the United States (2012) and the establishment of a similar regime by the European Union (2020), targeted human rights sanctions have emerged as a significant and increasingly institutionalized tool in transatlantic foreign policy. This research conducts a comparative analysis of the U.S. and EU Magnitsky sanctions frameworks, focusing specifically on their application in the case of Iran. How do institutional design differences between the US and EU influence Magnitsky sanctions implementation, and what implications do these variations hold for transatlantic human rights diplomacy? The analysis focuses on sanctions targeting Iranian officials as a comprehensive case study. The research hypothesis posits that divergent institutional architectures—U.S. executive-centered authority versus EU consensus-based decision-making—produce systematic variations in sanctions timing, scope, legal standards, and strategic integration. These differences reflect broader constitutional traditions fundamentally shaping human rights diplomacy approaches. Employing a comparative methodology to assess the logic behind the design and implementation of each sanctions regime. The analysis reveals that institutional diversity creates both coordination challenges and complementary capabilities in transatlantic relations. While American institutions enable swift comprehensive responses, European frameworks produce legally sustainable, multilaterally legitimate measures. Effective cooperation requires sophisticated coordination mechanisms leveraging institutional complementary .