In the U.S., overdoses have become a health crisis in both public and private places. We describe the impact of the overdose crisis in public libraries across five U.S. states, and the front-line response of public library workers. We conducted a cross-sectional survey, inviting one worker to respond at each public library in five randomly selected states (CO, CT, FL, MI, and VA), querying participants regarding substance use and overdose in their communities and institutions, and their preparedness to respond. We describe substance use and overdose patterns, as well as correlates of naloxone uptake, in public libraries. Participating library staff (N = 356) reported witnessing alcohol use (45%) and injection drug use (14%) in their libraries in the previous month. Across states surveyed, 12% of respondents reported at least one on-site overdose in the prior year, ranging from a low of 10% in MI to a high of 17% in FL. There was wide variation across states in naloxone uptake at libraries, ranging from 0% of represented libraries in FL to 33% in CO. Prior on-site overdose was associated with higher odds of naloxone uptake by the library (OR 2.5, 95% CI 1.1–5.7). Although 24% of respondents had attended a training regarding substance use in the prior year, over 90% of respondents wanted to receive additional training on the topic. Public health professionals should partner with public libraries to expand and strengthen substance use outreach and overdose prevention efforts.