Psychological capital (PsyCap) is a multidimensional psychological resource that has emerged in the organizational literature and received notable attention due to its solid theoretical foundation, valid and reliable measures, impact on work-related outcomes, and evidence of malleability and developmental potential. However, to date, positivity in general, and more specifically PsyCap applications, in the public sector remain scarce in the literature. This chapter explores some of these unique applications. After a general overview of PsyCap, including its definition, constituent resources, underlying mechanisms, and development processes, PsyCap is applied to four specific public sector contexts in the United States: fire departments, the Air Force, K-12 education, and higher education. The four case studies showcase specific practices and dynamics that can foster positivity and PsyCap, as well as challenges that can hinder PsyCap development.