This research aims to explain members' online brand community (OBC) engagement and participation based on their relationships with other members and with the community sponsor. It proposes a conceptual model integrating variables that have been studied in previous research on brand trust, OBC identification, and satisfaction, and others that have received little or no research attention, including the OBC sponsor's opportunism, sponsor's control, and OBC experience, with OBC engagement playing a key role. The conceptual model has been tested by applying structural equation modelling to a database of 628 consumers belonging to over 260 different online brand communities OBC from diverse economic sectors: for example, brands involving sports (Adidas and Nike), fashion (Mango, Stradivarius and Zara) and technology (Apple, Samsung and Sony). In general, the authors conclude the importance of engagement in explaining a member's involvement in a community, and the important role played by antecedents such as online brand community experience and trust, not only directly but also indirectly via identification with the community. The results confirm the influence of engagement upon a member's participation in a community. Our study supports this direction of the relationship over the reverse – participation engagement – as suggested by other previous works. With regard to the antecedents of trust in the online brand community, it has been concluded that using the community for mainly commercial purposes has a negative effect.