Increased urbanisation and climate change are negatively affecting the water cycle and are increasing floods and creating concerns for the built environment and human wellbeing. This has created a need to research sustainable water management in cities. Nature-based solutions (NBS) can offer more sustainable ways of water management, but conventional systems are still favoured in governance. Hence, the aim of this thesis is to identify opportunities and challenges of implementing NBS at Årstafältet in Stockholm and the related governance processes from a Socio-Ecological-Technical system perspective in order to bring a holistic view on sustainable urban stormwater management. The methods used in triangulation for this case study are interviews, a site visit, and desktop study of associated planning documents. The collected data is analysed with an analytical framework that investigates the Social-Ecological-Technical System (SETS) dimensions, in relation to governance. The results show that the implementation of NBS at Årstafältet has been largely successful, due to contextual factors, as well as an adaptive and reflexive governance approach. However, identified system dynamics, interrelations and tensions have shown that there is room for improvements. By increasing transdisciplinarity in early stages of the process to overcome rigid governance structures and techno-centricity. The application of the SETS framework has proved to be successful in identifying dynamics, interrelations, and tensions but there are issues related to uncertainties in how to categorise system components. Nevertheless, the SETS perspective has been useful for identifying challenges and opportunities related to governance and planning processes of implementing NBS.