People experiencing homelessness (PEH) are more often affected by mental illness. Different forms of poverty and socioeconomic inequalities in societies are closely connected to mental health, raising ethical issues for all parties involved in the care of people with serious mental illness (SMI). The implementation of inter- and transdisciplinary approaches and actions in mental health care and policy making related to poverty so far is scarce. This chapter provides insights into aspects of poverty and its effects on mental health of persons with SMI living in high-income countries. Approaching this topic, we will consider poverty on three levels: The micro-, meso- and macro-level, which we operationalize as the individual, the neighborhood-related and the societal level. Within this framework, we will apply four main medical ethical principles: respect for autonomy, nonmaleficence, beneficence, and justice. We close this chapter by reflecting on practical measures and policies to promote the mental health care of persons with SMI living in poverty. In this chapter, we will not discuss etiological aspects of poverty on mental health.