This study examines the potential for alternative and social media to stimulate the core antecedents of protest participation (identity, efficacy, and anger) in the context of Hong Kong’s pro-democracy movement. Findings from a representative sample supported the social identity model of collective action (SIMCA), such that all antecedents predicted intended protest participation. Identity and anger mediated the relationship between online alternative news and protest intention, while anger and efficacy mediated the relationship between social media news and protest intention. The findings demonstrate the benefits of theoretical integration from related disciplines to better understand the mobilizing potential of collective action through news media use.