Socially just, intergenerational urban spaces should not only accommodate children and adolescents, but engage them as participants in the planning and design of welcoming spaces. With this goal, city agencies in Boulder, Colorado, the Boulder Valley School District, the Children, Youth and Environments Center at the University of Colorado, and a number of community organizations have been working in partnership to integrate young people’s ideas and concerns into the redesign of parks and civic areas and the identification of issues for city planning. Underlying their work is a commitment to the Convention on the Rights of the Child and children’s rights to active citizenship from a young age. This paper describes approaches used to engage with young people and methods of participation, and reflects on lessons learned about how to most effectively involve youth from underrepresented populations and embed diverse youth voices into the culture of city planning.