Rejecting the "techno-utopianism" and "social media centralism" in traditional social movement studies, this study emphasizes the multidimensionality of the media and the context of the movement. Mainly using the research methods of ethnography and interviews, this study takes the Umbrella Movement as a case study, to investigate the media practices and mobilizing structures in Hong Kong's specific sociopolitical context. This work proposes an alternative framework of contextualized transmedia mobilization to explore how protestors situated in a specific context employ, create, circulate, amplify, and converge various forms of media to continually mobilize themselves and the public, and, thus heighten participation levels, innovate contentious repertoires, and experiment with organizational transformation.