The efforts of agroecology-oriented farmers and peasants’ orga-nizations have been studied in depth in relation to their political expression, but less so with regard to the forms they adopt to strengthen the socio-economic viability of small- and medium- sized farms within sustainable food systems. Whilst farmers’ self- organization represents a core process in the development of Agroecology-based Local Agri-food Systems (ALAS), the devel-opment of collective, economic structures among agroecology- oriented farmers’ is still weak. In an attempt to understand why and how agroecology-oriented farmers are constructing their own position within ALAS, and the challenges they are facing in this sense, we conducted a qualitative study on the self- organizational processes and structures of five Agroecology- Oriented Farmers’ Groups in Spain. Based on 27 interviews and six online, participatory workshops, our results reveal different reasons for joining and setting up farmers’ groups as non-mixed collective spaces, with instrumental and social factors constitut-ing the principal motivations. Politics and advocacy aroused controversy and were only observed in the biggest, most powerful and well-structured organizations. The main chal-lenges identified refer to the precariousness and isolation of farmers, as well as of the different local groups. The weakness of the Agroecology-Oriented Farmers’ Groups highlights the need for further action-oriented research and accompaniment