Nature-based Solutions (NbS) are an effective tool to reduce urban vulnerability to climate risks and, at the same time, develop more liveable urban areas. While existing research supports NbS' positive influence on urban climate adaptation, the extent of their impact remains insufficiently studied. Understanding the magnitude of NbS impact is crucial for justifying their preference over non-NbS alternatives and, consequently, for securing public investment. Via a meta-analysis, this paper aims to contribute to research and practice by providing a more systematic assessment of NbS effects, offering urban planners and decision-makers a robust justification for their incorporation in climate change adaptation, urban resilience, and enhanced liveability.