This study examines the effect of social networks and central figures in networks on information diffusion. Exploiting a government subsidy program and training workshops regarding the fair-trade and organic farming certifications in Sri Lanka, we conducted a randomized experiment to investigate the role of farmers’ social networks and “key farmers” in information transmission to workshop non-participants and their application to the certifications. Key farmers are agricultural village leaders unofficially appointed by local government officials. The estimation results show that key farmers’ involvement in the workshop amplifies information diffusion through social networks. In the treatment villages with key farmers involved, non-participants increase their knowledge of certifications and the likelihood of being a member of the applicant organization when directly connected with key farmers in their networks. Moreover, they are more likely to receive information goods from other peers in the network. However, in the control villages with key farmers uninvolved, direct connections with key farmers and farmers’ networks do not influence the diffusion of information goods and knowledge and participation in the applicant group. These findings suggest that central figures’ involvement is the key to the success of network-based programs.