This graduate thesis deals with analysis of the development of ecotourism in Istrian County. Ecotourism is one of the selective forms of tourism in which tourists stay in a natural and unpolluted environment, especially in protected areas. Goals of ecotourism are contributing to the sustainable development of a certain area and local community, minimizing negative effects in that area and raising awareness of the importance of environmental protection. Characteristics of ecotourism are described in this paper. Also, behavior of ecotourists and their activities during the travel are explained. The historical development of ecotourism is described. Ecotourism in Istrian County takes place in protected natural areas, although not all features of ecotourism are fulfilled there. The Istrian County is rich in protected natural areas and they will all be described in this paper. Tourist valorization of protected areas is analyzed with selected examples of Brijuni National Park and Učka Nature Park. It is analyzed if the visitors are satisfied with their visit in natural protected areas. Also, at the end there is SWOT analysis of ecotourism in Istrian County. This paper confirms initial hypotheses that in Istrian County there are a lot of protected natural areas but they are not properly valorized for tourism. Istrian County has a big potential for developing ecotourism that would contribute to the sustainable development of this touristic destination.