Urban watercourses are often affected by hydrological, chemical, and ecological degradation, driven by increased impervious surface cover in an urban environment, impact on flow regimes, and diffuse pollution. Among the most persistent challenges are elevated loads of total suspended solids, heavy metals, nutrients, organic micropollutants, and microbial contaminants transported by stormwater runoff. These pollutants contribute to oxygen exhaustion, eutrophication, bioaccumulation of toxic substances, and substantial losses in aquatic biodiversity. In response to these pressures, nature-based solutions are increasingly applied as decentralised and ecologically integrated strategies for improving water quality. This review presents full-scale applications of NbS, analyzing their technical characteristics, pollutant removal efficiencies, and ecosystem service benefits. The results indicate that the removal of TSS often exceeds 80%, while the reductions vary depending on the design of the system, the type of vegetation, and hydraulic loading rates. In addition to improving water quality, these systems contribute to flood retention, habitat creation, temperature regulation, and carbon sequestration. Despite their multifunctionality, the implementation of NbS remains challenging due to regulatory fragmentation, design uncertainty under changing climate scenarios, and the lack of standardized monitoring protocols. The primary objective is to provide a comparative overview of full-scale nature-based systems applicable to improving water quality and supporting the ecological restoration of urban streams affected by climate change and intensive land use.