To describe the Medicaid costs associated with persons who are homeless or unstably housed. A retrospective secondary data analysis linked Medicaid recipient data with a statewide homeless management information system. A total of 19,950 persons received a housing service between 2012 and 2015 including 14,136 persons with Medicaid. Five of the most frequent diagnoses were substance abuse or mental health conditions in 42.83% of all diagnoses. The most frequent service was outpatient mental health and emergency department physician services. These costs totaled $166,653,689 with prescription drug costs at $62,800,463, with a total cost of $672,242,449, averaging $14,632.42 per 12-month period per person. The potential changes in Medicaid could lead to cost transfers or a reduction in services. Recognizing these are significant costs by homeless and unstably housed persons only, these high costs warrant the determination of points in care where effective cost saving interventions may be employed.