Third-party sexual harassment, perpetrated against employees by individuals external to their employing organization, is a serious and all too common issue faced by employees in service-oriented occupations. This includes sexual harassment of library employees by library patrons. Studies in service-oriented industries, such as retail and hospitality, have demonstrated that most instances of patron-perpetrated sexual harassment go unreported, and that employees often feel obligated to react to these occurrences with informal responses that often further perpetuate the problem. This presentation will explore some of the factors that contribute to the prevalence of patron-perpetrated sexual harassment in libraries, as well as factors that cause the issue to be under-reported and under-addressed in LIS workplaces, education, and literature. It will also provide suggestions on how library workers and administrators can recognize, address, and prevent patron-perpetrated sexual harassment in their workplaces.