Purpose - This study aims to examine the relationship between social influence and consumers' self-expression through brands. It considers susceptibility to interpersonal influence and social network influence on self-expressive brands and brand tribalism. The study examines whether self-expressive brands and brand tribalism influence brand loyalty and word of mouth (WOM).Design/methodology/approach - A cross-sectional online survey was carried out with members of Generation Y in Ireland. Data from 675 complete responses were analysed using SPSS 20 and AMOS 20. A structural model tested nine hypothesised relationships.Findings - Findings indicate that both online social network influence and susceptibility to interpersonal influence are antecedents of tribalism and self-expressive brands. Consumers of self-expressive brands are loyal and offer positive WOM. By contrast, those who seek tribal membership have less brand loyalty and offer less WOM than other consumers. Findings suggest that consumers may be loyal to tribes, rather than to brands. This informs our understanding of the role of tribes for consumers and brand outcomes.Research limitations/implications - This study is limited to Generation Y consumers within Ireland.Originality/value - This is the first study to explore the effect of consumers' perceptions about online social network influence on brand tribalism. In addition, their views about the influence of the social network on self-expressive brand consumption, and brand outcomes, are identified. This paper highlights consumers' susceptibility to interpersonal influence on their brand choices and brand tribalism. In addition, it is shown that brand loyalty and WOM are not always a consequence of tribal membership. By contrast, self-expressive brand consumption enhances brand WOM and brand loyalty.