Activist groups increasingly use computer-mediated communication (CMC) channels to mobilize large groups of consumers to persuade incumbent firms to change their contested strategies or practices. The attributes of CMC channels change the effectiveness of persuasion processes in organizations. Similarly, attributes may change the effectiveness of protest mobilization. Yet, organizational research to date has mostly neglected this potential effect. This paper systematically reviews the effect of CMC attributes on the antecedents of protest participation. We construct a conceptual framework based on social movement and media choice theory, which guides the systematic collation of online activism research. Three main themes emerge from the literature. First, we find that the interactivity of online activism decreases the need for formal mobilizing structures, while increasing the importance of informal mobilizing structures for protest diffusion and global cooperation between activist groups. Second, increased interactivity and user control provide an alternative media channel for consumers and resource-poor activist groups to express and bundle their grievances. Third, the degree of publicness and interactivity seems to stimulate the formation of multiple, online collective identities that are rather interest-based than identity-based. We conclude this paper with a conceptual model that highlights the most prominent relations found in literature and discuss the implications for future research and practitioners.