Homelessness is a major public health problem that has received considerable attention from clinicians, researchers, administrators, and policymakers in recent years. In 2016, 550,000 individuals were homeless in the United States (U.S. Department of Housing and Urban Development, 2016) with 4.2% of individuals in the United States experiencing homelessness for over 1 month sometime in their lives and 1.5% experiencing homelessness in the last year (Tsai, 2017). Homelessness remains a recalcitrant problem and a ripe area for study, particularly in addressing needs of individuals at high risk for homelessness and those from understudied populations. New and innovative measurement approaches, interventions, and study methodologies are presented in this special issue to shed light on how psychology can help benefit and improve homeless services.