The tolerance of mercenaries by the states of the world puts the security of humanity in extreme danger, facilitating the initiation and maintenance of armed conflicts on the world map. Among the preventive measures, most frequently implemented by the criminal legislation of European states, is the criminalization and criminal punishment of mercenary activity. However, for the effective prevention of mercenaries, it is not enough to adopt incriminating and repressive models. It is still necessary to substantiate and develop preventive criminological measures, which are to be implemented at the national and international levels. The theoretical foundation of these preventive measures must be based on the exact knowledge of the criminological factors generating mercenary activity. In this study, the authors identify and analyze the possible criminogenic factors that determine or facilitate the commission of mercenaries, with special reference to the Republic of Moldova and the former states of the ex-Soviet space.