Kony2012 was a viral Internet video that attracted unprecedented online interest in promoting a campaign to arrest the leader of an African militant group. The current research considers the social psychological bases of social media-based collective action. In three cross-sectional surveys (N=304) collected before, on, and after the key action date of 20 April 2012, we consider the nature (opinion based or global) and function (emergent or transforming) of social identity in modern forms of social action. Multigroup structural equation modelling showed that Kony2012 action was best captured by an emergent opinion-based social identity. Moreover, the same factors that predicted Kony2012 action generally also predicted engagement in new repertoires of protest (involving the use of social media) and an observable traditional socio-political action (signing a letter to a government minister). The results suggest that there is no sharp dividing line between traditional and new forms of collective action and that both may be understood as valid expressions of collective selfhood.