Taking up TRUSTMAKING as an active and applicable response to the challenges of living together in cities, this research project aims to empower urban youth and build capacities of city governments for the new green transition. Establishing a trustful basis is key for well-informed, intergenerational, and cross-sector collaboration with city governments, entrepreneurs, and civil society organizations during urban development processes. Through Place-making practices we aim at fostering confidence of youth to co-create urban spaces, working in and with green infrastructures in four European cities: Oslo (Norway), Panevėžys (Lithuania), Vienna (Austria), and Valkenswaard (The Netherlands). Through Urban Living Labs, tools for youth co-creation of green infrastructure are identified and developed, and cross-section collaboration mechanisms are designed in summer/winter schools. Lastly, the development of TRUSTMAKING guidelines addresses capacity building in public service for integrating youth perspectives and competences that bridge short-term concerns and long-term objectives in urban transformation.