Rosario, Argentina, a city of more than one million people strategically located on the Paraná River in the heart of a fertile agricultural region, is home to a significant industrial corridor where ongoing urbanization for industry, including that associated with the port complex and agroexport industries, vies for real estate space with peri-urban and urban farming production. The city is also the site of thriving municipal programs seeking to change food production and consumption outcomes through urban and peri-urban agriculture projects rooted in agroecology. This paper identifies the socio-natures critical for the formation and endurance of these agroecology assemblages. Based on interviews with 30 stakeholders in government, civil society, and agricultural production, we describe the integrated approach to environmental, social, and economic sustainability embedded in Rosario's institutional agroecology programs. In particular, we discuss the actors and strategies (which seek to preserve land for agricultural uses), discursive renderings of socio-natures (as valuable biodiverse territories and productive diverse bodies), and the marketing of agroecological materialities (through production for public markets) that form and are formed by these assemblages. We also discuss the power dynamics embedded in sustaining urban and peri-urban agroecological projects through institutional means. This research contributes to literature on agroecology, urban agriculture, and the urban metabolism through providing empirical examples of socio-natural entanglements in urban agroecological assemblages.