Despite decades of effort, biodiversity has not attracted effective political discourse, policies, or action to halt its decline. In cities in particular, biodiversity conservation is challenged by short-term approaches, separately focusing on biodiversity or community well-being rather than on their interconnection, and pervasive beliefs that urban citizenry lack the requisite ethic or skills for conservation action or biodiversity governance. We describe how a systemic co-inquiry in Victoria Australia, conducted by citizen and agency practitioners alongside policy developers and academic researchers, modified understandings, practices, and institutional arrangements (governance) for urban biodiversity conservation. The most impactful outcomes of the early co-inquiry period were (1) start-up funding for a network to forge collaborations between community and local government actors that engage urban residents in supporting indigenous biodiversity in their gardens, and (2) empowered co-inquiry members driving the network's development. These efforts have led to on-going social learning and longterm institutional arrangements for a burgeoning network of municipally based nature stewardship collaborations that are nurturing local human-nature relations. Key challenges include(d): maintaining the co-inquiry, paradigms that undervalue urban biodiversity and the role of citizens, organizational inertia, and evaluation measures incommensurate with strengthening person-nature relationships. Our research shows how systemic co-inquiry involving citizen practitioners can surface misleading assumptions around biodiversity stewardship and governance, and help to empower citizen and agency actors to focus on nurturing sustainable human-nature relations in cities.