The population of geriatric homeless individuals diagnosed with serious mental illness is a largely underrepresented subpopulation in the research literature despite the notion that this population is one of the most vulnerable to negative outcomes due to physical, mental, and psychosocial factors. This chapter briefly summarizes the separate impact of each of these three factors: being homeless, being in the geriatric population, and being diagnosed with a serious mental illness (SMI). In addition, the chapter illustrates how these three factors combined impact overall subjective quality of life and poor outcomes for mental health through the use of a case vignette of a homeless, geriatric individual with a severe mental illness. It also provides case example illustrating that high comorbid substance abuse along with an SMI (i.e., dual diagnosis) associated with complex medical conditions create seemingly insurmountable challenges for the interdisciplinary care team.