This paper is concerned with the role of network administrative organizations (NAOs) in the development of social capital in inter-organizational networks aiming at supporting their members to innovate in the food sector through interacting with one another. A multi-case study approach is used whereby three Belgian inter-organizational networks are investigated i.e. Wagralim, Réseau-Club and Flanders Food. Our study shows that there are many options available to NAOs to build social capital within the networks they are responsible for; options which we propose to categorize in three main distinct groups: creation of boundary objects, careful selection of members and effective communication.