Sexual assault affects a large proportion of women in the world. Although most rapes are committed by one man, the act itself may be influenced by many (e.g., the peer group). Hostile sexism (HS) has repeatedly been associated with men’s rape proclivity, but the influence exerted by the HS of the peer group on rape proclivity has not been investigated. In this study, we explored the impact of perceived male peer support to HS on participants’ rape proclivity. A sample of Spanish undergraduate students from a university in the south of Spain (N = 134) completed the Ambivalent Sexism Inventory. Immediately afterwards, they received feedback on the supposed sexist responses of a peer group (high vs. low in HS); we kept the benevolent sexism (BS) of the peer group at medium levels. Next, we assessed participants’ rape proclivity using acquaintance rape scenarios. Results showed an interaction between participants’ own levels of HS and information about the HS of the peer group. Men high in HS reported higher rape proclivity in the high-HS peer-group condition than in the low-HS peer-group condition. By contrast, information on the peer group did not affect self-reported rape proclivity of men low in HS. Results also corroborated the relationship between participants’ levels of HS and rape proclivity, and expanded the literature by revealing an unexpected influence of participants’ BS on rape proclivity.