We examined factors associated with frequent hospitalizations and emergency department (ED) visits among Medicaid members who were homeless. We included 6494 Massachusetts Medicaid members who received services from a health care for the homeless program in 2010. We used negative binomial regression to examine variables associated with frequent utilization. Approximately one third of the study population had at least 1 hospitalization and two thirds had 1 or more ED visits. More than 70% of hospitalizations and ED visits were incurred by only 12% and 21% of these members, respectively. Homeless individuals with co-occurring mental illness and substance use disorders were at greatest risk for frequent hospitalizations and ED visits (e.g., incidence rate ratios IRRs = 2.9-13.8 for hospitalizations). Individuals living on the streets also had significantly higher utilization (IRR = 1.5). Despite having insurance coverage, homeless Medicaid members experienced frequent hospitalizations and ED visits. States could consider provisions under the Patient Protection and Affordable Care Act (e.g., Medicaid expansion and Health Homes) jointly with housing programs to meet the needs of homeless individuals, which may improve the quality and cost effectiveness of care.