Smart cities could help overcome traditional problems of big cities, such as pollution, traffic congestion and administrative corruption. They can stimulate economic productivity, accommodate population growth, and make lives more convenient, but at the same time, they raise many security threats to national security. Daily life needs in smart cities are based on information and communication technologies. Houses, infrastructure, transportation, communication, government services, as well as commercial and industrial services, etc. are controlled by smart systems dependent upon artificial intelligence and the Internet of things1. If these services are targeted by a successful cyber-attack, the consequences in that case would be unaffordable to national security and to people’s lives. This article seeks to analyse the impact of smart cities on national security, and it comes in three main sections. The first one defines smart cities and its different models, the second one analyses the impact of adopting the smart city model on national security, and the conclusion tries to provide some recommendations of how to decrease national security risks in the smart city.