Purpose: This article aims to contribute to building an understanding of how social media may support farmers in transition to a more sustainable agriculture. Methodology: We used a questionnaire survey and in-depth interviews with farmers concerned with sustainability issues to characterize the diversity of their social media (SM) uses and user profiles. Findings: We show widespread but also very contrasting uses of SM by farmers concerned with sustainability issues, combining epistemic and socio-emotional dimensions. Practical implications: We propose several implications for facilitators of online and in-person groups dedicated to supporting farmers engaged in sustainability transitions. Theoretical implications: The use that farmers concerned with sustainability issues make of SM supports an integrated view of farmers' transitions to sustainability as processes that are not only technical but also involve many variable dimensions. Our understanding would therefore benefit from further analyzing SM users as virtual communities of practice (COPv). Originality: Rather than focusing on one SM, we start from farmers' uses of various SM, which provides an original perspective on SM in agriculture. It also contributes to filling in the gap in knowledge about digital tools' potential contribution to sustainability.