This study examines the guarantees that are granted to the accused during investigation before the International Criminal Court by analyzing the relevant texts to the subject in the Basic Statute of the International Criminal Court and comparing them with what is stated for in the Omani Law, treaties and other international instruments. Its subjects analyze the historical development of the establishment of the International Criminal Court, as well as its jurisdictions and the penalties it rules by, up till its emergence as a permanent international criminal body. Further, the study goes on to demonstrate the guarantees of the accused during investigation that constitute an obligation upon the concerned authority, and then comes across the guarantees that exist as a right for the accused regarding which the view of the researcher is provided. Furthermore, this study demonstrates the scope of these guarantees and the extent to which the Basic Statute of the International Criminal Court has gone in adopting guarantees that are ignored by the national systems. Hence, it evaluates the extent of efficiency of these guarantees and the aspects of their weaknesses and advantages in contrast with the Omani Law. Finally, the study finishes with a conclusion that includes results and recommendations to ensure the protection of the rights of the accused at this important stage in the hierarchy of the lawsuit