Urban micro-farms are therefore intermediate forms that lie between community gardens and vegetable farms recognised as such by their profession and the agricultural authorities. Despite their growth, urban micro-farms in France remain limited in number, and their heterogeneity does not allow a unique typology to be outlined. In order to differentiate them, the main activity of the structure is of interest. Drawing inspiration from the tools for assessing agricultural sustainability, this study generated an original reading grid to understand the functioning of these urban micro-farms. It took 18 months of participatory research, including numerous surveys of producers, follow-up and the collection of field data concerning production, production costs and revenue and working time. Projects must therefore integrate work organisation adapted to the project objectives, continuous and quality access to resources and a stable and solid partnership network. It is often the farmers themselves, the project leaders, who are the keystone of an urban micro-farm’s longevity.