This study quantifies drivers and consequences of positive and negative electronic word-of-mouth (eWOM) engagement on social networking sites building upon social identity theory. Fitting a structural model using software smartPLS 4.0, the analysis compares two distinct groups of respondents. Though these groups seem to belong to the same in-group. Nevertheless, group members differ with respect to the drivers and consequences of their positive and negative eWOM engagement. As engagement is often used in the context of service-dominant logic, we reveal which non-monetary value co-creating and value-reducing consequences result from positive and negative eWOM engagement. This study highlights the impact of eWOM engagement on self-brand connection and self-brand incongruity and identifies commitment as a major driver. For international respondents negative eWOM does not automatically increase self-brand incongruity but low negative eWOM has a positive effect on the self-brand connection.