From a governance perspective, sovereign states used to hold the authority of performing certain functions for the sake of 'public interest' but recently governments have begun to share this authority with non-state actors. In this article, 'security governance' defines the network which constitutes co-operation between the states on the one hand and military service providers as non-state actors on the other. The purpose of this article, from the perspective of security governance, is to analyze the role of private military companies in the field of international security in order to fill a gap in international relations theory to some extent. The first part introduces the differences between governance and government and the concept of security governance. The second part explains in turn the private military sector, classification of the sector, its historical background, activities, and services. The third part discusses the legal status of their military activities and the normative dimension. Finally, all matters relating to private military companies are subjected to an overall evaluation from the conceptual perspective of security governance. Consequently, private military companies are the only actor of the international system in security governance offering military services by contract.