Ensuring and guaranteeing the defense rights of the accused is the cause of a fair trial, which are equally mentioned in the laws of Iran and France. Because, it is at this stage that the foundations of the case are formed for the realization of criminal justice. The Code of Criminal Procedure, adopted in 2013, has new facilities in order to protect the rights of the accused under its supervision and guarantees. These developments are broader than the previous law. But the main challenge of these developments is the lack of effective control and supervision or the lack of effective enforcement guarantees regarding the observance of the rights of the accused being monitored. The presence of a lawyer in the criminal process, in addition to being known as an assistant judge, is also beneficial in the administration of justice and securing the rights of the accused, and this issue is considered by the legislators of Iran and France. In this study, an attempt is made to review the role of the lawyer in guaranteeing the defense rights of the accused in the face of officers and the judicial authority in the Iranian and French legal systems