Despite the fact that sexism is an inherently intergroup phenomenon, women's group-level responses to sexism have received relatively little empirical attention. We examine the intergroup reactions experienced by 114 female students at a U.S. university in New England who imagined being a bystander to a sexist cat-call remark or control greeting. Results indicate that women experienced greater negative intergroup emotions and motivations towards the outgroup of men after overhearing the cat-call remark. Further, the experience of group-based anger mediated the relationship between the effect of study condition on the motivation to move against, or oppose, men. Results indicate that bystanders can be affected by sexism and highlights how the collective groups of men and women can be implicated in individual instances of sexism.