Research on the psychological and marketing-related predictors of bystanders’ intentions to intervene when consumers are bullied in online brand communities is scarce. Using Structural Equation Modelling and Process Analysis, we investigate bystanders’ concern for social appropriateness as key psychological influence that drives intervention intentions, and further consider two novel moderators. Specifically, when brand followers perceive the victim to be a rival, the effect of social appropriateness on intention to intervene is weaker than when the victim is a supporter. Moreover, when brand followers perceive the community to have a stronger consciousness of kind, the effect of social appropriateness on intention to intervene is more emphasised compared to when the consciousness of kind is perceived to be lower. The same is true for the moderation effect of shared rituals and sense of moral responsibility. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.