The Internet and Web 2.0 have created novel forms of collective action and political participation, the dynamics of which have attracted considerable scholarly attention. E-petitioning, a genre of technology-based collective action tools, makes it possible for members of the public to address government decision makers directly with their requests for policy-related action. In this paper we explore the effects of Twitter, other forms of online media, and television news broadcasts on the accumulation of signatures in e-petitioning. We analyze the case of “Bring Back Our Girls,” a Change.org petition initiated in spring 2014 following the abduction of 276 young female students from the Government Girls Secondary School in Chibok, Borno State, Nigeria by heavily armed members of the Boko Haram, an Islamic extremist group. The petition targeted government leaders around the world. We found evidence that tweets and certain forms of online media, together with cable news items, are related to the likelihood of individuals to sign an e-petition. The results provide evidence in support of a hybrid media system in which diverse forms of media behave with diverse logics and impacts in their effects on e-petitions. •In this time series case study, Tweets issued over time were related to signature accumulation.•Cable TV news and other online news items were also related to signature accumulation.•Online items that mentioned the petition were also related to signature accumulation.•The results show evidence of traditional agenda setting as well as reverse agenda setting.•The results show effects of platform design on signature accumulation.