The high energy demand and the threat of climate change have led to a remarkable development of renewable energies, initially through technologies applied to the terrestrial environment and, recently, through the awakening of marine renewable energies. However, the development of these types of projects is often hampered by failure to pass the corresponding environmental impact assessment process. The complexity of working in the marine environment and the uncertainties associated with assessing the impacts of such projects make it difficult to carry out objective and precise environmental impact assessments. AMBEMAR-DSS seeks to establish a basis for understanding and agreement between the different stakeholders (project developers, public administrations, environmental organizations and the public in general), in order to find solutions that allow the development of marine renewable energies, minimizing their environmental cost. For this purpose, a DSS is proposed which, based on cartographic information and using objective and quantifiable criteria, allows comparative assessments and analyses between different project alternatives. The analytical procedures used by the system include, among others, hydrodynamic modeling tools and visual impact simulators. In addition, impacts on marine species are assessed taking into account intrinsic ecological and biological aspects. The magnitude of the impacts is quantified by means of fuzzy logic operations and the integration of all the elements is carried out by an interactive multi-criteria analysis. The results are shown in tables, graphs and figures of easy interpretation and can be also visualized geographically by means of a cartographic viewer. The system identifies the main impacts generated in the different phases of the project and allows establishing adequate mitigation measures in search of optimized solutions. The establishment of the assessment criteria has been based on the abundant, but dispersed, scientific literature on the various elements of the system and having the opinion of experts in the various fields. Nevertheless, the DSS developed constitutes a preliminary basis on which to build and improve a system with the input of researchers, promoters and experts from different disciplines.