This study presents a replicable method to assess the multi-benefit performance of Nature-based Solutions (NbS) for urban stormwater management. Applied at seven sites across Northern Europe, the study measured flood reduction, water quality, cooling, and public well-being. Water quality improvements were highest at sites with large surface areas and extended flow paths, and benefit–cost ratios ranged from 1.28 to 3.62. This study provides practical, site-specific evidence to guide resilient NbS investments.