Public libraries are often considered welcoming spaces for people experiencing homelessness. For people experiencing homelessness, the public library offers a warm place to stay in the winter, and a cool place to spend time in the summer, as well as a variety of information services. In 1990, a lawsuit filed by Richard Kreimer against the city of Morristown, New Jersey reinvigorated discussions around the role of public libraries in providing services to people experiencing homelessness. I use boundary work theory to explore the experiences of public library workers as they provide health and social services information to people experiencing homelessness. Boundary work refers to the situations or activities in which public library staff are creating, negotiating, reinforcing, or crossing boundaries (Gieryn, 1983, 1999). In this dissertation, I focus on the following overarching question: How do public library staff perform boundary work when providing health and social services information to people experiencing homelessness? To address this question, I look at the major areas around which public library staff perform boundary work and the functions of boundary work for the profession of public librarianship. I conducted interviews with 24 public library staff at three library systems and conducted directed qualitative content analysis to develop a theoretical framework of public library workers’ boundary work. This study demonstrates that library staff perform boundary work around: identifying who experiences homelessness, issues of privacy, professional roles, organizational structures, and professional discourse. The analysis also reveals that public library workers rely on boundary work to legitimize their profession, their professional roles and responsibilities, and to define what it means to be a public librarian in comparison to other fields—namely social work, PREVIEW ii and health. In the discussion, I also develop a theoretical framework of public library staff and their performance of boundary work. I conclude by arguing that public librarianship is indeed experiencing change and that it perceives itself as overlapping with social work in ways that it does with health professions. By performing boundary work, public library staff cope with change, articulate their expertise, and consider potential directions for the future of the profession.