This research examines the role of colleagues’ helping behavior in workplace bullying. Although colleagues are often able to intervene to support the victim or stop the bullying, passive behavior and nonintervention are more frequent. The bystander effect described by Latané and Darley (1970) has been studied in the context of school bullying and sexual harassment, but only rarely has it been studied in the context of workplace bullying. We tested the influence of the belief in a just world for others, self-efficacy, perceived severity, and causal attribution as determinants of three types of bystander helping behavior. We used a vignette describing a case of bullying in a vertically organized workplace in an online questionnaire survey, which was completed by 194 workers. The results showed that low self-efficacy was associated with nonintervention, that perceived severity mainly determined public helping behavior, and that both internal and external causal attributions contributed to explaining both emotional and public support for the harassed colleague. The results highlight the importance of training to increase awareness and recognition of bullying phenomena among colleagues.