Compared with more productive areas, mountain areas are at risk of being marginalized, particularly in the agri-food sector. To circumvent price competition, local actors in the mountains can develop specialized local products, which depends on their capacity to act collectively. Collective action, however, is complex and needs to be better understood if it is to steer initiatives towards success. This article sets out a relational approach to studying collective action in a dairy cooperative located in a mountain area: The Primiero cooperative in the Italian Alps. The common pool resources and territorial proximity frameworks were combined in a social network analysis of advice interactions among producer members, and an analysis of trust and conflict among members and between members and other actors involved in the value chain. The results show that the success of collective action can be explained by various complementary factors. Firstly, members had dense relationships, with high levels of trust and reciprocity, while the president had the role of prestige-based leader. Nonetheless, the analysis also highlighted conflicts related to the production levels of “traditional” and “intensive” producers, although members demonstrated a high capacity to resolve conflicts by creating their own rules to control further intensification. Socio-economic status did not appear to play a role in advice relationships, showing that the members interact horizontally. However, the results show that the geographical isolation of some members tended to inhibit their commitment to the collective dynamics. At a higher level, trust toward other actors involved in the value chain plays a central role in carrying out joint projects to develop and promote cheese.