This research brief provides information on what is known about the factors associated with prolonged homelessness among youth, including involvement in the child welfare and criminal justice systems; histories of child maltreatment; substance use and mental health challenges; unstable housing and living situations; and family relationships, health, behavioral, and demographic factors. Studies indicate associations between all of these risk factors and prolonged homelessness among youth. Other factors associated with prolonged homelessness include a history of running away from a family home, group home, or foster home; differences in religious beliefs between youth and parents/guardians/caregivers; risky sexual behaviors; and low-self control. Little research examining whether there is a link between prolonged youth homelessness and subsequent adult homelessness, indicating the need for additional research. Policy makers should consider youth rates of system involvement and behavioral health challenges when designing strategies to prevent and end prolonged homelessness.