Hundreds of grassroots protests have taken place across the United States under the banner of the Black Lives Matter (BLM) movement since 2013. This paper examines the public Twitter feeds of six social movement organizations (SMOs) affiliated with the Black Lives Matter (BLM) movement in order to ascertain the nature of the movement from the standpoint of theories of contentious politics. The main finding from the three content analysis studies presented in the paper is that the core activists of the BLM movement use Twitter primarily for expressive communication. Another key finding is that the SMOs examined in this study generated more tweets that framed the movement using the rights-based language of liberalims than frames about gender, racial, and LGBTQ identities. Finally, the SMOs rarely used Twitter to mobilize their followers to engage in contentious politics. Moreover, when they do seek to mobilize their adherents, they tend to do so with an eye toward stimulating participation in the extant political system.