The decline in ecosystem services (ES) across the world is mostly associated with land use change, which is the basic outcome of ecosystem degradation. The changes associated with land use development often negatively impact ecosystems to sustain their services. The lack of capability of contemporary land suitability (overlay) analysis on ES-based decision support approach necessitates a new way of analytical method integrating ES to promote sustainability more efficiently in spatial decision making and ecosystem management. Although there is a growing attention on ES-based data improvement and spatialization of ES data through mapping and valuation at local and global levels, the configuration of analytical decision support tool of ES has not been developed yet to be used for spatial decision-making purposes. In this paper, a case study for the application of ES-based decision support approach is presented to contribute as a spatial decision support tool. Duzce, a province distinguished with being another major drinking water supplier of Istanbul, is selected as a case. The aim of the paper is to explore the relevancy of ES-based land suitability (ESLS) assessment approach as a decision support tool in spatial decision making by comparing with the contemporary land suitability (overlay) analysis. Both approaches have been developed and superimposed with multilayered/multi-functional spatial assessments to achieve an integrated final output separately. The findings of the research prove that ES-based analytical approach for spatial decision making can better formulate and contribute to more holistic and comprehensive spatial decision making.