Research has repeatedly confirmed that farmer field schools can serve as a bridge between science and farm practice, enhancing simultaneously rural social energy. However, even though social capital is a burgeoning topic in FFS research, it is not clear whether and how it mediates FFS performance. In this mixed-methods study, using data from two FFS projects conducted in Greece, we examined if social capital among trainees facilitates the co-creation of knowledge and the co-development of agricultural innovations by farmers. A thematic (...) analysis was performed to analyse qualitative data, whereas regression models were employed for the quantitative strand of analysis. Results revealed that social capital evolves progressively during FFS, enabling the achievement of the project’s aims by enhancing in-group communication, establishing affective ties, instilling a sense of community, and triggering motivational contagion among participants. Statistical analyses confirmed that the “softest” sides of social capital significantly contribute to knowledge and innovation co-production. Although this work was based on data derived only from two FFS projects that took place in Greece, our findings underline the importance of social capital for the success of any FFS project and emphasise the need for identifying routes to nurture social capital within FFS. (shrink)