We applied a communication as constitutive of organizing (CCO) perspective in a case study to examine Twitter’s influence on the leadership dynamics in the 2019 Hong Kong Protests. We argue that Twitter is a powerful nonhuman leadership actor by demonstrating how it coordinates a plenum of co-participating agencies to construct meaningful narratives. In addition, we show that while many social movements call themselves leaderless, because of Twitter’s co-participation, they are not leadership-less. Using digital methods, we first harvested movement-relevant tweets based on hashtags and retweet counts from a key event of the protests, and then analysed the video content in the three most-retweeted tweets. Our analysis shows that Twitter’s various mechanisms dictate how online conversations unfold, and that Twitter therefore influences how “authoritative text” is established. Our study contributes to the literature in three ways. First, we contribute to critical leadership studies by showing that Twitter is a leadership actor that enacts sociomaterial leadership, which further challenges the dominant human-centric and masculine views of leadership. In doing so, we reveal that the persistent leaderless movement narrative is a fantasy. Second, by illustrating how Twitter’s authorship mechanisms generate authority and polarity, we contribute to a stream of CCO studies showing that platforms influence power dynamics. Third, by attending to multivocality and dissensus, where a myriad of voices could speak up against the established and perceived injustice, we assert that Twitter as a leadership actor dictates specific modes of communication with performative effects.