In this day and age, one of the specific ways of responding to organized crime is covert operations which, as a measure of an undercover investigation, are a very important form of legal and criminalistic actions. The most efficient tactic of covert operations is deploying an undercover investigator. The success of undercover agent missions is reliant on meticulous planning of every stage of the investigation, in this way the actions of undercover agents can prevent the future criminal activity of suspects and members of criminal organizations. The research subject of this paper encompasses the criminal procedure analysis of an undercover investigator in the legislation of the United States of America and the United Kingdom. This paper aims to compare the legal framework of commissioning an undercover investigator in two compatible legal systems to identify the elements that differentiate between these models and the legal solution in the Republic of Serbia. In the conclusion, we highlight the advantages and disadvantages of the observed differences.