Global urbanization trends have made people move to cities where they tend to have less access to nature. Urban nature is important for human well-being and biodiversity, therefore urban planners are increasingly integrating Nature-based Solutions (NbS) projects in urban environments.  This research investigated how to support citizen engagement for NbS while evaluating the urban environment, focusing on young people as they are often excluded from decision-making and planning processes.  The research design included a literature review and interviews with city planners, to develop a Participatory Photo Mapping (PPM) tool to enhance resident participation and stimulate discussion around social and environmental aspects for effective urban NbS.  The prototype tool consists of a multi-layer map combined with NbS projects, locations, and photos reported by participants (from two Swedish cities, Malmö and Karlskrona), and two environmental indicators: land cover and biodiversity occurrence. Participants identified locations they perceived as improving or hindering the quality of life and the natural environment.  Participants valued ‘nature’ as the key multi-beneficial factor for the socio-ecological systems. The prototype supports strategic sustainable development by allowing holistic mapping and evaluation of the city to increase communication between the residents and municipalities and to strengthen residents’ engagement in shaping their cities.