Why do states commit to UN counterterrorism treaties? This article posits that state accession to UN counterterrorism treaties is likely informed by the nature of the terrorist threats a state faces, and consequently, the pressures that such threats generate from domestic and international audiences on the state to address (or appear to address) them. As such, we hypothesize that states ratify UN CT treaties for either material, needs-based reasons—to gain external assistance for counterterror capacity building—or for symbolic reasons—to visibly signal their commitment to fight terrorism in order maintain legitimacy, and mitigate reputational costs to both domestic and international audiences. To test these hypotheses, we use a newly compiled dataset of state accessions to the 19 UN counterterrorism treaties from 1970–2016, testing both our needs-based versus symbolic hypotheses, as well as more “traditional” explanations for state treaty accession. Across the universe of 19 UN counterterrorism treaties, our study implies that states may be more likely to ratify treaties as mechanisms to signal intent to address terror threats rather than to build threat-specific counterterrorism capacity. This research thus broadens both academic and policy-related understandings of state counterterror treaty ratification.