The principle of equality of arms is considered one of the fundamental foundations of a fair trial, which guarantees equality between the parties to the dispute in terms of facilities, rights and opportunities for defense. This principle is particularly important in international criminal proceedings, because defendants are often in an unequal position when faced with international judicial bodies and the extensive capabilities of the prosecution. In the International Criminal Court (ICC), although the Statute of the ICC addresses this principle in articles such as 54, 61 and 67, several challenges are observed in its implementation, especially at the preliminary investigation stage. The absence of an independent investigating judge, the extent of the prosecutor's powers, and the limitation on the disclosure of evidence are among the factors that can affect the balance of the proceedings. In addition, Article 69(7) of the Statute of the ICC establishes the rule of inadmissibility of evidence to prevent the admission of evidence obtained through violations of fundamental rights, but its practical implementation still faces obstacles. This article, by examining the principles, challenges and solutions to achieve equality of arms in the preliminary investigation phase of the ICC, shows that for this principle to be truly realized, it is necessary to pay attention to the independence of the investigation process, more careful monitoring of the disclosure of evidence and facilitating access to counsel for the accused in order to better guarantee the principle of equality of arms.