Studies report higher levels of spectator aggression at the end rather than the beginning of sports games. None of these studies have examined the effect of chanting in this context. Based on contagion theory, we hypothesized that at the end of a football (soccer) game, spectators who had taken part in collective chanting would report higher levels of aggression than would spectators who had not chanted. Male football fans (N = 80) participated in the study: Half completed the Buss–Durkee Hostility Inventory before the game, and half completed it after the game. Findings show that chanting spectators reported a heightened level of aggression in comparison with non-chanting spectators. Theoretical explanations for these findings are discussed. Practical recommendations are suggested.