Over the past decade, new municipalism has emerged as an alternative form of politics emphasising radical democracy and community-based urban agendas. However, recent election results and challenges in navigating existing institutional frameworks worldwide have prompted a further examination of the potential and limitations of new municipalism in different contexts. This article evaluates the implementation of new municipal governance in Valparaíso, Chile, where a neighbourhood organisation backed by the local government clashed with a developer seeking to privatise and redevelop a critical ecological area called Pümpin Park. The city's significant public park shortage led to widespread social unrest, protests, and legal inquiries. Using firsthand accounts and official records, this study analyses how Valparaíso practices new municipalism by collaborating with grassroots movements to achieve the project's cancellation. However, it is still unclear whether the municipality's long-term urban development plans will continue to reflect a new municipalist agenda beyond this particular conflict.