Cities are breeding spaces for innovations in the agro-food sector with the potential to foster the development of local niche networks and a food sustainability transition. In this paper, we propose a conceptual framework for the context-related development of urban food niche organizations and their networks of change agents. With a qualitative analysis of three niche-establishing organizations and their networks, we address the lack of knowledge on spatial-relational dynamics shaping the development of niche organizations and their networks. The identified dynamics are structured along the connotations of geographic, cognitive, social and institutional proximity within the niche networks, to the to the dominant actors, rules, and practices of the urban food system's regime and to society. For each niche network, we defined a strategic orientation that might lead to a specific development path. Finally, we propose strategies on how cities may foster the development of niche organizations and their networks to highlight local opportunities of supporting a food system sustainability transition, i.e., increasing food literacy, enabling access to space, and engaging in networking.