This study relies on semi-structured interviews with twenty-four public library staff to understand how they navigate professional boundaries when providing information services to people experiencing homelessness. Analysis of the interviews indicated that public library staff perform work related to managing their professional roles and responsibilities, particularly in the context of the public library as a third, or transitional space. This boundary work refers to situations or activities in which actors construct, manage, and challenge professional boundaries, as originally described by Gieryn [13]. The results of the interviews show that public library staff perform boundary work as it relates to the public library as a third space, or transitional space, used by any number of community members and as I argue, particularly by those experiencing homelessness. In the case of public librarians' provision of information services to people experiencing homelessness, the library acts a day shelter or transitional space, which has several implications for the public library and for the staff.