Nature-based solutions can help to reduce climate change-induced hydrometeorological hazards and their damage, while supporting biodiversity and providing ecosystem services. A major difficulty comes in identifying appropriate indicators and metrics for assessing the effectiveness of NBSs. This chapter presents an application of cost-benefit analysis in evaluating the economic efficiency of NBSs to reduce hydrometeorological risks. It evaluates selected NBSs to reduce flooding, landslides, and nutrient loading of waterbodies in five areas, considering the costs of their establishment and implementation, the benefits due to reduced hydrometeorological risks, and the co-benefits from additional nonmarket impacts on biodiversity and ecosystem services. This chapter applies several methods to identify both the cobenefits of NBSs and to define how their monetary value would improve the reliability of the approach. For most NBSs, the CBA indicates that benefits are higher than their costs. However, there is still considerable uncertainty about the biophysical and economic impacts of NBSs, in particular for the valuation of biodiversity benefits. The chapter shows that CBA is useful as a systematic and transparent approach for assessing the efficiency of NBSs from society’s viewpoint.