Afghanistan is one of the most complex and exceptional countries in the world. For decades, it has faced persistent instability and political crises. Following the events of September 11 and the intervention of the international community—particularly the United States—it was widely anticipated that the process of nation-state building in Afghanistan would succeed. However, despite extensive international efforts over the past two decades, the collapse of the republican system demonstrated the failure of this process. The primary question of this study is why nation-state building in Afghanistan did not materialize and what factors hindered its development. The objective of this research is to examine the major challenges that have acted as obstacles to the nation-state building process in post-2001 Afghanistan. This study employs a descriptive-analytical approach. The findings reveal that Afghan society, shaped by a tribal political culture and religiously duty-oriented beliefs, has consistently impeded the nation-state building process. In addition, ethnic politics, the absence of a cohesive national identity, power monopolization, and administrative corruption have been among the most significant factors contributing to instability and the failure of nation-state building in the country.