Football-related violence (hooliganism) is a global problem. Previous work has proposed that hooliganism is an expression of social maladjustment. Here we test an alternative hypothesis, that hooliganism is typically motivated by a parochial form of prosociality, the evolutionary origins of which may lie in intergroup raiding and warfare. In a survey of Brazilian football fans (N = 465), results suggest that fan violence is fostered by intense social cohesion (identity fusion) combined with perceptions of chronic outgroup threats. In contrast, maladjustment is unrelated to indices of past acts of football-related violence or endorsement of future violence. Our results suggest that to reduce hooliganism and other forms of inter-group violence, efforts could be made to harness the extreme pro-group sentiments associated with identity fusion in more peaceful ways.