This study aims to explore multiple factors that are associated with social media use by public librarians for marketing purposes. Based on the technology acceptance model and theory of planned behavior, the effects of five factors-usefulness, ease of use, attitude, subjective norms, and behavioral control-on social media use intention were examined. A survey was conducted, and 462 valid responses were collected from public librarians across the United States. The findings revealed that all five factors have a significant impact on librarians' intention to engage in social media activities for library marketing. Perceived behavioral control factors were the most influential on social media use intention. Both practical and theoretical implications are discussed based on the findings of this study. S ocial media has emerged as an essential marketing outlet for public libraries to interact and communicate with patrons online. Social media is an internet-based tool designed to support social interactions among users in real time or asynchronously, and it enables individual users and organizations to create their profile pages and to contribute and share content on online networks (Boyd and Ellison 2007; Bertot, Jaeger, and Hansen 2012; Carr and Hayes 2015). Many public libraries have actively utilized social media channels to communicate with patrons and to increase visibility in online environments (Rogers 2012; Luo, Wang, and Han 2013). As a low-cost marketing tool, it is advantageous in that it can increase efficiency, interactivity, feedback from users, community engagement, sense of community, and