This study aims to examine the very fabrics of underground sport betting system that is associated with match-fixing. Mafia, syndicates, and bookmakers are the three levels of actors in the hierarchy. Having grassroots bookmakers as our particular focus, we examine their roles and networks, what regulates the system, and how the system functions. Thanks to our academic links with the mafia, we had access to bookmakers to carry out observations and 25 interviews. We rely on the social capital model in which structural, relational and cognitive dimensions are identified. Findings reveal that actors are empowered by their social capital to streamline their underground business. Far from the stereotype of a competitive market under the control and coercion of very powerful mafia, our observations of bookmakers, mainly women, show that they cooperate, trust each other, and have great autonomy in their activities. Because of their strong shared culture and networks, betting activities are considered acceptable in their own small community.