Homelessness among unaccompanied youth is a unique, yet pervasive, social problem. Youth often become homeless through three central pathways: conflict with family, involvement in the foster system, and involvement in juvenile justice systems. As youth experience homelessness during important developmental period(s), vulnerability to mental illness may occur if not already present. The present study examined the type and prevalence of mental illness. Characteristics of homelessness, health and mental health service utilization, and pathways to homelessness were examined in relation to the occurrence of mental illness. Findings indicated that a variety of characteristics are associated with mental illness. Mental health service utilization was also evaluated.