In response to multiple ecological, climatic, and social challenges in cities, nature-based solutions (NbS) are increasingly promoted to support sustainable and resilient urban futures. Despite their potential, effective application of NbS requires a clear and systematic understanding of their effectiveness in addressing urban challenges. This thesis assesses the effectiveness of urban NbS for biodiversity and human well-being and examines how evidence can support NbS decision-making. It first builds a global evidence base of 547 empirical urban NbS cases. The assessment shows that NbS generally produce positive effects compared with non-NbS alternatives, although performance varies with NbS type, outcome domain, [...]