Terrorism in the global world is recognized as one of the most significant threats. Hence, combating terrorism has become a primary focus for security professionals throughout the world. By studying the phenomenon of modern terrorism, we can easily conclude that the nature of terrorism has changed. Therefore, the authors are focused in the article on a new form of terrorism, named “environmental terrorism”. Environmental terrorism is an old type of conflict with a new face, and we have to confront it. For the purpose of this article the authors have chosen to present the environmental terrorism threat to the Serbian water infrastructure sector. The available scientific data witnessed that the water infrastructure system in Serbia is already vulnerable and needs a lot of improvement. A terrorist attack on such a fragile infrastructure could have enormous consequences and be devastating in its scope. Hence, the authors have analyzed the current state in the water infrastructure sector, which is already compromised with numerous problems and have addressed the question: do we fully understand the water infrastructure vulnerabilities and what has to be done to ensure its protection as one of the part of the Serbian critical infrastructure? The protection of the water infrastructure sector against terrorist attacks is a task for the Serbian Government, but it has to be solved in collaboration with neighboring countries. The final goal for all activities has to be the greater scope of trust among the neighbors and the achievement of an adequate level of security regarding environmental terrorism threats in the region of South Eastern Europe. Furthermore, environmental terrorism as a threat has to be settled at a national and regional security agenda in a more visible way.