Implementing Nature-Based Solutions (NBS) in the urban context represents the current challenge and opportunity to address environmental, social and economic issues. This typology of interventions is encouraged by international and national policies, like the European Green Deal, the Sustainable Development Goals (SDGs) and the Italian National Recovery and Resilience Plan (PNRR), according to NBS’s capacity to provide multidimensional benefits. However, despite this great interest, the operative implementation of NBS interventions in urban planning is quite limited and fragmented. This is mainly due to the lack of a suitable decision-support tool to sustain NBS design and planning in the urban context according to specific needs, as well as the limited estimation of both costs and benefits related to NBS interventions in monetary terms. This research proposes the definition of an integrated evaluation tool which combines the Spatial Multicriteria Analysis (SMCA) with the Cost Benefit Analysis (CBA) to fill the addressed evaluation gaps. SMCA is applied to identify the most urgent intervention area according to multidimensional vulnerability criteria. CBA is applied to estimate the costs and benefits of NBS interventions. This article illustrates the methodological background of the proposed evaluation tool, describing its purpose and possible evaluation application. The proposed evaluation framework represents an operative Decision Support System (DSS) which supports decision-makers to efficiently use the economic resources by identifying the most urgent intervention area for NBS implementation, giving information about the community feasibility of the NBS intervention.