Framed within theories of fairness and stress, the current paper examines bystanders’ intervention intention to workplace bullying across two studies based on international employee samples (N = 578). Using a vignette-based design, we examined the role of bullying mode (offline vs. online), bullying type (personal vs. work-related) and target closeness (friend vs. work colleague) on bystanders’ behavioural intentions to respond, to sympathise with the victim (defender role), to reinforce the perpetrator (prosecutor role) or to be ambivalent (commuter role). Results illustrated a pattern of the influence of mode and type on bystander intentions. Bystanders were least likely to support the victim and more likely to agree with perpetrator actions for cyberbullying and work-related acts. Tentatively, support emerged for the effect of target closeness on bystander intentions. Although effect sizes were small, when the target was a friend, bystanders tended to be more likely to act and defend the victim and less likely to reinforce the perpetrator. Implications for research and the potential for bystander education are discussed.