PurposeThis study investigates the mechanism of defensive word-of-mouth (WOM), which refers to consumers responding to unfair negative online reviews of a brand with which they identify.Design/methodology/approachStudy 1 employs an experimental design that manipulates brand identification and the perceived fairness of negative WOM, using a gift card choice scenario to measure decision-making behavior. Study 2 involves a real event with Google reviews and follows a quasi-experimental design, manipulating identification with the university and using Google Maps star ratings to measure brand attitude.FindingsConsumers with high brand identification are more likely to defend the brand when confronted with unfair negative WOM. However, they do not always exhibit defensive WOM in fair cases. Furthermore, the results show that the defensive WOM can strengthen consumers’ brand attitude and supportive behavior.Practical implicationsEncouraging defensive WOM by mobilizing brand advocates and highlighting the unfairness of negative WOM could be a practical strategy to defend the brand and minimize the risk of online firestorms. Notably, defensive WOM itself strengthens the relationship between consumers and the brand.Originality/valueThis study proposes a mechanism for the defensive WOM phenomenon and demonstrates that the rebound effect in brand attitude caused by negative WOM comes from consumers’ willingness to express defensive WOM. We draw on self-affirmation theory to address the gap in theoretical explanations for defensive WOM. This contributes to the literature on self-identity and WOM research by showing that consumers defend their identities through WOM communication.