A growing body of research examines variables that may improve or impede helpful bystander action to prevent peer sexual assault among adolescents. The current study examines how individual and relational variables distinguish youth who respond to sexual violence in unhelpful versus helpful ways. Students were given a survey to assess frequency of actions taken in response to four peer sexual violence situations. Helpful actions were more likely among students who endorsed positive bystander attitudes and who reported more proactive prevention behaviors and less likely among students who self-reported peer violence perpetration. The findings support bystander prevention efforts that change social norms, increase proactive behaviors, and promote responsibility for intervening. Effectiveness may be enhanced through tailored approaches for youth most at risk for unhelpful bystander responses.