Sexual assault continues to plague college campuses despite years of targeted intervention. Recent prevention efforts have focused on the role of bystanders in reducing rates. However, limited work has explored actual intervention behaviors as opposed to intentions to intervene or reasons why individuals might choose not to help. College students (N = 1219; aged 19-62; 66% women) completed an online survey assessing experiences as a bystander witnessing a sexual assault, willingness to intervene, helping behavior, and associated beliefs and attitudes (rape myth attitudes, perceived peer norms, perceived self-efficacy). Fifteen percent witnessed a recent situation that they believed involved sexual assault, and most students (69%) intervened. Lower rape myth endorsement, greater self-efficacy regarding intervening, and greater perceived norms that peers would intervene on behalf of a peer predicted willingness to intervene. A personal history of sexual assault and knowing of another's assault increased the odds of perceiving an assault was underway. Knowing the victim increased the odds of intervening for all groups except men. Reports were compared among students who identified as men, women, heterosexuals, and sexual minorities. This research advances our understanding of how common it is to witness sexual assault, who is willing to intervene, and cognitive-affective barriers to intervention among college students. Specific recommendations for practitioners and educators are provided.