The obligation to extradite or prosecute criminals and defendants by the contracting governments is one of the issues affecting the judicial assistance of the governments. Domestic laws and extradition treaties are the most important sources of extradition that, in case of conflict between the two, according to the principle of precedence of international law over domestic law, international agreements take precedence over domestic law. In any case, the high volume of treaties between governments in the field of extradition shows that this obligation can become mandatory, but despite the necessity of including the rule of extradition, there are exceptions that create obstacles in the implementation of extradition. Some of these obstacles are legal considerations, others are due to extradition procedures, and some are related to human rights. The condition of mutual criminality, exclusivity of extradition (rule of exclusivity), prohibition of extradition of domestic citizens, prohibition of extradition in political crimes are examples of prohibition of extradition. In this research, the obstacles to the extradition of criminals have been investigated with a descriptive-analytical method, and finally, suggested solutions to overcome these obstacles have been presented.