Sport‐related violence is widespread. Yet, there is a poor understanding of what factors trigger hooligans to become unruly. In this paper I test the so called frustration‐aggression hypothesis, which holds that thwarted expectations from a reference point tend to lead to violent behavior. I use unique data on hooligan violence in Sweden. I find that frustration, generated by a team's bad performance, indeed leads to unruly supporter behavior. A one‐position drop in the soccer league leads to approximately 5 percent more unruly behavior by the team's supporters. The analysis helps policy makers in their endeavors to reduce group‐related violence.