Abstract Issue Urban green spaces are necessary for developing healthy and sustainable cities. Benefits of Nature-based solutions (NBS) that increase the amount and quality of urban green go beyond environmental aspects (noise/air pollution mitigation) and have positive impact on mental health, active lifestyles and social cohesion. However, there is a need for the transdisciplinary co-creation processes including multidisciplinary partners and local community to ensure that different population groups use NBS and that health, social and environmental benefits are maximised. The Horizon2020 project CLEVER Cities (2018-2023) focuses on the development of NBS in deprived areas to address health, socio-economic and ecological challenges in a transdisciplinary co-creation approach. Description The three pilot cities, Hamburg, London and Milan, have formed Urban Innovation Partnerships (UIP) based on the stakeholder mapping. Each UIP involves citizens, companies, universities and local authorities to support CLEVER Action Labs (CAL) as alliances of local actors involved in the co-creation and assessment of place-based NBS interventions. The Theory of Change method (impact chain) was used to structure the transdisciplinary process, by initially determining the desired long-term outcomes related to the above-mentioned challenges. Proceeding from the identification of the local conditions, the necessary “outputs” were identified to achieve short-term and intermediate outcomes, which themselves lead to the determined long-term outcomes. Results/lessons Preliminary results show that Theory of Change provides a good structure for transdisciplinary discussions as well as an overview of a complex transformative change, underlying assumptions and unintended negative effects. Involving urban public health experts is essential to determine the relationship between different NBS and health outcomes, to maximize health benefits for all population groups and to reduce potential side effects. Key messages Inclusion of local community in the collaborative co-creation process is essential to ensure that NBS is adapted to their needs and that the desired health and wellbeing outcomes are achieved. The involvement of urban public health experts in the Theory of Change is essential to raise the awareness about the relationship between NBS interventions, their use and multiple health outcomes.