Water pollution poses a significant and escalating threat to urban environments, particularly in the rapidly expanding cities of Asia. Addressing this challenge requires implementing cost-effective solutions, and one such approach is the deployment of Nature-based Solutions (NbS) to treat septic tank effluents, canals and lakes. This study represents a pivotal step in this direction by formulating a comprehensive framework to assess the effectiveness and impacts of NbS. The research draws on six case studies spanning the Philippines, Sri Lanka and Vietnam, offering valuable insights into the practical application of NbS in diverse urban contexts. Furthermore, the study has yielded practical guidelines for the construction and installation of three key NbS components: Constructed Wetlands (CWs), Constructed Floating Wetlands (CFWs), and Green Roofs (GRs). These guidelines were implemented through trial implementations, enhancing our understanding of their real-world performance. Moreover, stakeholder engagement played a vital role in this endeavour, as such gatherings provided essential data on public acceptance and the influence of policies and governance structures. The knowledge and insights from these interactions contribute significantly to the collective understanding of effectively replicating and implementing NbS for water treatment in urban environments. The project successfully trained 72 early career professionals and students from project partners and stakeholders. It produced 23 publications, including a book, book chapters, journal articles, perspectives, resource materials reports and four short videos on NbS. These outcomes were achieved through the collaborative efforts of project partners and stakeholders, engaging in 29 events such as quarterly, national and regional meetings, field trips, focus group discussions, socio-economic surveys and extensive field trials.