The activities of intermediary organisations in the context of payments for agri-environmental services have broadly increased in all European countries over the last two decades. However, the impact of this new governance mechanism on environmental protection and changes in individuals' behavior has not yet been studied in the economic literature. To explore this issue, we develop a new theoretical economic framework that allows us to compare the main environmental effects of an incentive mechanism with intermediaries, such as environmental knowledge brokers and information providers, as compared to those of a standard central governance mechanism. This paper bridges the knowledge-brokering theory developed in the literature in environmental science with the process of individual preferences formation and transmission developed in the economic literature. The analysis shows that the emergence of knowledge intermediaries is particularly valuable in the context of payments for agri-environmental services in a situation where individuals, such as farmers, initially have a low level of environmental awareness. The same conclusion holds when the public institution organizing the scheme is not sufficiently apprised of individuals' characteristics. This allows us to give a theoretical justification for previous empirical results on payment schemes for agri-environmental measures.