Management of economic use of maritime domain in Croatia is uncontrolled, lacking theoretical and scientific support, as well as practical application of the relevant factors of growth and development that affect not only the development of maritime systems and the entire Croatian maritime system, but complementary activities as well. System development of these activities should be redefined on local, regional and national level. Accordingly, the fundamental objective and purpose of this thesis is to consistently analyse, elaborate and appropriately resolve the possibility of redefining the economic use of maritime domain in development and sustainability of complementary activities, which is a fundamental prerequisite for accelerated development of the complex maritime economy as an integral part of the over-all national Croatian economy. The scientific hypothesis at the core of this project is: Using scientifically obtained insights about the functioning of economic use of maritime domain and development concepts of complementary activities with respect to modern trends and harmonious development of all sectors of maritime economy, it is possible to propose a model of sustainable development of complementary activities related to the economic use of Croatian maritime domain which would ensure rational management and growth and development of the maritime and transport system in Croatia. To prove the set scientific hypotheses, a combination of scientific methods was used, including methods of analysis and synthesis, concretization method , mathematical methods, methods of descriptive and inferential statistics and the matrix method of growth as one of the methods of evaluation and assessment of sustainable development of complementary activities in the maritime domain . The proposed model consists of four basic sub-models and although very complex, it can serve as a good basis for making quality strategic, tactical and operational decisions regarding the sustainable approach to economic use of maritime resources. The main findings of this study can be summarized as following: all the elements of dynamic model of sustainable development of complementary activities in the maritime domain (logistic, social, environmental and security) should achieve significant growth rates in the future to improve the quality of economic exploitation of maritime domain in accordance with the principles of sustainability.