The purpose of the study was to observe how public libraries’ communication on Twitter has been changed before, during, and after the COVID-19 outbreak. A total of 40 active, public library Twitter accounts were used for data collection and analysis. The tweets examined were a combination of original tweets ( n = 2623) and retweets ( n = 666) posted from other Twitter accounts on the public libraries’ Twitter feeds. A content analysis scheme was used to analyze topical aspects of the tweets. The study found that public libraries were more active in communicating information on social media during the COVID-19 lockdown period. Promoting library events/programs, communicating library operations to patrons, and highlighting library resources for literacy are common in public libraries’ Twitter communication throughout the 3 years period. The study also observed strong associations between the content types of posts and the contextual aspects of the libraries, including an emergency situation such as the COVID-19 lockdown, the size of the population served by the library, and the state in which the library was located. In other words, the study provides evidence that public libraries use different communication strategies on Twitter depending on factors such as community emergencies, service population size, or geographic location. The results of this study illustrate that through social media usage, public libraries demonstrate their competence as public agencies in managing their services, as well as their commitment to the core value of information access and service provision to users, even in the face of unprecedented crises.