Research has shown that micro-mobilization efforts that invoke social media rely heavily on the influence of personal networks to motivate collective action participation. This study examines whether this trend applies (a) to networks of different levels of personalness, (b) to causes and organizations which people are either unaware of or not affiliated with, and (c) how personal networks affect people's willingness to participate in online versus offline forms of collective action, when personal dispositional factors (activism- and issue involvement, perceived self-, technological-, and group efficacies) are considered. An experiment (N = 315) tested whether calls-to-action by different sources via social media (close personal networks v. distant social networks v. organization officials) influence individuals’ willingness to publicly express support online through social media-based collective activities (e.g. commenting, hyperlinking, ‘Liking’, etc.) and offline activities (e.g. demonstrations, donning campaign materials, etc.). Findings are leveraged to provide practical insight and to inform theoretical development in these domains.