Public security was unable to achieve any systematic order until the start of urbanization. With the formation of modern cities, the need to ensure the security of people and their living spaces were met primarily by city administrators and then by regular internal security organizations. This article discusses Iran’s security system as it existed in the pre-modern period and the internal security strategies that transformed in line with the modern understanding of the state. The concept of internal security in Iran has gone through the following four main phases: (1) military methods that had been applied by the senior administrators of the states that had ruled the region before the Qajar Dynasty, (2) the first professionalization that saw the Nazmiyya Organization established in the Qajar Dynasty through efforts to separate policing from military service, (3) the re-militarization of internal security services and focus on intelligence activities during the Pahlavi Dynasty that had been established after the Rıza Han coup, and (4) the ideological appearance of the police organization accompanied by the theo-political orientation that emerged after the 1979 Revolution. This text discusses these four phases in detail.