The right of access to a lawyer is one of the recognized human rights and one of the guarantees of the right to a fair trial. The main question of this article is what are the challenges of the right of access to a lawyer in international human rights and Iran's judicial system?And what are the consequences of limiting it in criminal proceedings?And on that basis, with a comparative study,in the position of answering these questions,it will come up with a descriptive and analytical method.According to the findings of the research,the mechanism of identifying and guaranteeing the right of access to a lawyer in the aforementioned legal systems,despite the similarities between them are different and do not have the same legal guarantees,and despite its recognition as one of the criteria of the right to a fair trial, the said right in International human rights are temporarily and repeatedly restricted in the normal laws of Iran's judicial system and are accompanied by numerous judicial challenges in order to access them,and on this basis,the legal challenges of the right to access to a lawyer in these systems It will limit it in criminal proceedings and by denying and limiting the voluntary choice of a lawyer, it will lead to the violation of the right to access to criminal justice and the unfairness of the proceedings,and the effective recognition and guarantee of the right to access to a lawyer will also be the basis for the realization of criminal justice and fair proceedings