This paper discusses the role of cities and local governments in the implementation of strategies for sustainable urban food systems. In six Mediterranean metropolitan regions we analyze urban policies and agricultural practices, along with the political processes involved. The comparison confirms that cities are pertinent actors, capable of encouraging new practices and transversal governance. Nevertheless, questions remain concerning their ability to mobilize the agricultural community, and civil society in general, both elements crucial to the sustainability of any agricultural and food strategy. In concluding, we discuss the conditions that could lead to the emergence and implementation of sustainable urban food systems.