This research evaluated a community-led participatory planning process that sought to involve citizens who are often marginalized within planning processes. Participatory planning – which is theoretically informed by communicative planning theory – may shift the legacy of power and marginalization within planning processes and improve planning outcomes, foster social cohesion, and enhance the quality of urban life. The two-year Stewart Street Active Neighbourhoods Canada (ANC) project aimed to build capacity among residents of a low-income neighbourhood in Peterborough, Ontario and to influence City planning processes impacting the neighbourhood. The project, led by a community-based organization, GreenUP, fostered collaborative interactions between residents and planning experts and supported residents to build and leverage collective power within planning processes. The participatory planning approach applied in the Stewart Street ANC transformed – and at times unintentionally reproduced – inequitable power relations within the planning process. Importantly, we found that GreenUP was a vital power broker between marginalized residents and more formal power holders, and successfully supported residents to voice their collective visions within professionalized planning contexts.