The introduction of marine spatial planning (hereafter: MSP) for Croatia is essential, considering the coastline length and the increasing usurpation of coastal and marine space. MSP is more than a process that regulates the activities on the sea. It is an analytical approach to the setup of human activities in the marine area. As a maritime country, Croatia has ratified the Protocol on Integrated Coastal Zone Management and undertook the obligations of the Barcelona Convention. However, an appropriate document has not yet been made that would enable quality management of marine space. MSP and its onshore version contribute to the establishment and development of various activities, taking into account environmental, natural, economic, and sociological criteria. MSP is a continuation of spatial planning of the mainland area and must undoubtedly consider the more expansive coastal environment and the activities there. One of the tools in marine area mapping is the Geographic Information System (GIS), which has proven to be a very high quality and effective tool, especially in decision-making processes. The authors analyze the existing legal framework for marine spatial planning. Particular emphasis is placed on the obligations facing the Republic of Croatia to implement marine spatial planning. Given that the paper seeks to determine the advantages of MSP implementation using modern tools in marine area mapping, the authors in the third part discuss the benefits of using GIS as an acceptable tool in mapping marine space and provide recommendations for further actions.