Facing the modern forms of crime committed by criminal organizations and criminals, the world is presented with a great challenge in collective security and protection of the fundamental interests of citizens. In Macau, with the development and exploitation of game of chance, the Special Administrative Region has become more important on the world stage. On one hand, such progress has brought many economic advances to the society. But on the other hand, as the number of tourists and foreign workers increases, the number of complex and highly organized crimes also tends to increase. The traditional methods of investigation are becoming inefficient, unfit for combating crime adequately. In these situations, new forms of combating and prevention of crime, which were not necessary, are now required, such as agent provocateurs (in Portuguese, “agentes provocadores”), covert agents (“agentes infiltrados”), and undercover agents (“agentes encobertos”). It seems to me that these new forms of police intervention in criminal investigation deserve a deeper understanding, therefore, I take the opportunity to address and analyze this topic in my dissertation. Given that this topic is rather large, my analysis is focused on the legal regime of proof obtained by agent provocateurs. As the analysis on the legal regime of proof obtained by agent provocateurs depends on the knowledge of agent provocateurs and the like, it is necessary for the dissertation to touch on these notions simultaneously. Based on this rationale, my dissertation is presented in the following way. First, I start with a simple discourse on criminal investigation and the means of obtaining proof. Then it follows by a section written in the context of comparative law to develop the doctrinal and jurisprudential notion and understanding of agent provocateurs in various legal experiences, comparing it with covert agent and undercover agent. Lastly, I conclude with the validity of proof obtained by police agents in criminal process and the possibility of making use of the proof collected by agent provocateurs.