Intimate partner violence (IPV) is a prevalent problem worldwide. Friends of perpetrators may be in a unique position to support or affect change. However, little is known about the influence of friendship with a perpetrator on responses to IPV. Social identity theory describes an ingroup bias whereby ingroup perpetrators of violence are viewed as less personally responsible than outgroup perpetrators. This bias has been consistently found for impersonal ingroup relationships, but there is limited research in relation to friends of perpetrators. Drawing on social psychological theories, this study aimed to explore the impact of friendship with a perpetrator on responses to IPV—specifically, on attributions of causality and social rejection. A fictional vignette depicting IPV perpetrated by either a friend or a stranger was presented to 174 university students, who then completed a questionnaire on attributions and social rejection. Results indicated that participants attributed high blame to the perpetrator regardless of their relationship, but friends of the perpetrator were significantly more likely than strangers to attribute the cause of the violence to external factors. Friends of perpetrators were likely to continue the friendship, though social rejection was significantly more likely when the perpetrator was attributed high blame and internal causality. Ingroup bias was not consistently present across all outcomes, demonstrating the complexity of social relationships and IPV. The findings suggest expectancy based on past behavior may influence attributions for violence in existing relationships. The combination of high blame, external attributions, and low social rejection was discussed in relation to opportunities for friends to intervene to prevent IPV. The multifaceted influence of friendship on responses to IPV perpetration suggests the need to consider relationship factors when designing violence prevention campaigns and bystander intervention programs.