I examine a 2-week window into an environmental movement trying to gain traction in the public sphere, centered on a transnational day of action calling for a ban on the drilling technology, high-volume hydraulic fracturing, the Global Frackdown. Twitter serves a different purpose for the anti-fracking Global Frackdown movement than other Internet-based communications, most notably email listservs. Findings show that Global Frackdown tweeters engage in framing practices of movement convergence and solidarity, declarative and targeted engagement, prefabricated messaging, and multilingual tweeting. In contrast to Global Frackdown tweeters’ use of the platform for in-the-moment communication, Global Frackdown activists report in in-depth interviews that they place more emphasis on private (i.e., listservs) communication channels for longer term, durable movement building. The episodic, crowdsourced, and often personalized, transnational framing practices of Global Frackdown tweeters support core organizers’ goal of promoting the globalness of activism to ban fracking. This research extends past scholarship on socially mediated activism by providing a case study of how environmental activists use Twitter for ephemeral movement communication during a pre-planned transnational day of action, blurring internal movement collective identity-building and affirmation with publicly enacted strategic framing.