This article presents powers of prosecutors of international criminal tribunals during the pre-trial stage of criminal proceedings. It focuses on such institutions as power to initiate of proceedings and its limitations, preliminary examination of a case, authorization of investigation, conditions of such authorization and powers of the Prosecutor to act on a territory of states. It underlines the independence of the Prosecutor, which is a fundamental element of his status and is protected equally to independence of judges. It presents the conditions on which the Prosecutor can initiate a case – he not only can initiate criminal procedure proprio motu but also chooses situations and perpetrators that should be brought to justice before international tribunals. He should act on the basis of opportunity principle and take actions only in the most severe situations regarding most serious violations of international criminal law when specific circumstances indicate that they are in the interest of an international organ of justice. The article stresses that in the process of creation of international criminal tribunals not only criminal procedure sui generis was designed but also for the first time detailed powers of the Prosecutor had to be adapted to specificity of their functioning. The creators of international criminal tribunals applied legal instruments from several legal systems choosing solutions that seemed most appropriate for organs of international justice. In the consequence such procedure constitutes an amalgamate of common law institutions and solutions used in continental legal systems.