Legitimacy is a key but a-changing concept in political science. It has evolved in parallel with the changing political realities throughout history. In the current political environment, legitimacy of a political order depends on its approval by people at the domestic level. However, this domestic approval has to be sustained by an international approval, an attribute underlined especially during the Cold War era. Latin American crises of legitimacy and the more recent East European crises of legitimacy provide concrete examples for this. Hungary, as one of the East European countries which underwent the post-communist systemic transformation faces a renewed crisis of legitimacy. The grounds of legitimation have changed in comparison with the grounds of legitimation of the ancien regime, especially under the Kádárist rule. This thesis analyses the Kádárist attempts at legitimation, and then focuses on the post-communist system in Hungary to compare it with the ancien regime in search of the answer to the question what has changed during the transformation. This study focuses on legitimacy with its domestic and international dynamics, taking into consideration the systemic, institutional and social changes in the post-communist era. It concludes that a combination of political, economic and social improvements will ensure the new system’s legitimate status in both domestic and international arenas.