This article reviews the dynamic relationship between the media and the large-scale pro-democracy demonstrations in post-handover Hong Kong. It analyzes how the media have contributed to citizen participation, its roles in constructing the movement's self-understanding, and the impacts of the demonstrations on media discourses. The media and interpersonal networks are found to play instrumental roles in facilitating large-scale demonstrations, resulting in a mode of self-mobilization. Media discourse helps legitimize collective action as a way for citizens to express their opinions. The huge turnout in demonstrations narrowed the political parallelism of Hong Kong media. The huge rallies and subsequent events lent importance to the interactions between public discourse and collective action in Hong Kong.