National parks are defined as the most complex protected natural resources, they are mostly large spatial units that contain a high degree of preservation of unspoiled nature. They have been declared protected goods because their main goal is the protection of natural values in a certain area and the controlled use of the same for the needs of tourism, education and certain research. Thus, there is a need for sustainable tourism in such areas, which needs to be constantly developed, which is really not aneasy process. In national parks, sustainable tourism is very important, it encourages tourist packages with a certain emphasis on environmentally responsible actions and thus plays an important role in preserving the cultural heritage of local residents and thus contributes to the development of their economy. With the emergence of sustainable tourism, there are certain indicators of sustainability with which tourism is associated, and these are economic, environmental and socio-cultural indicators that are very important for the management of sustainable tourism. They are very important because they indicate possible problems in the development of tourism, in other words, they are a measure of risk and the need for action. For the purpose of theabove, a survey of the Krka National Park was conducted, which is one of the three most visited national parks in Croatia. NP Krka very intensively manages sustainable tourism, annual survey of visitors takes into account their remarks and strives to solve them, also the National Park Public Institution participates in many environmental -educational projects that help them to develop the park in accordance with the paradigm of sustainability. As the number of visitors to protected areas is increasing, it is very important to invest in the future development of sustainable tourism, which requires monitoring trends both locally and globally.