This paper aims to describe the process of farm biogas diffusion among mixed crops and livestock farmers in Indonesia. Social network analysis is applied to a case study in the Yogyakarta Province, to shed light on farmers’ knowledge networks. Primary data originate from a social network questionnaire administered to potential biogas adopters. Once mapped, networks were analyzed via the estimation of centrality measures. Consistent with previous literature about developing countries, study findings show that the farmers’ degree of connectivity is positively correlated with their likelihood to adopt farm biogas. Direct information exchange among neighbors may be effective in encouraging new adoptions. This research points out the existence of time lags between information retrieval and technology adoption which may be among the motives of the slow rate of farm biogas diffusion in the case study area, besides uneven understanding of the practical implications of biogas adoption. The availability of a structured network of extension services may speed up farm biogas diffusion among farmers in Yogyakarta.