In this study, private military companies (PMCs), which are used for fulfilling some functions of national armies, by both developed and failed states, are examined. The phenomenon of PMC open to discussion and redefine the limits of private and public sectors in general, and the limits of privatization and marketization in particular. Within this perspective, firstly new public management and governance theories are mentioned to explain the theoretical background of the study. Afterwards, PMCs are evaluated by using the criteria of political cost, national security and legacy. Finally, the development of PMCs in Turkey and administrative and legal regulation of this new topic are discussed and suggestions are made.