Background: Recognizing the role of social determinants in supporting overall health and achieving healthcare delivery transformation, the Maimonides Medical Center (MMC) Department of Population Health, with support from NYSHealth, studied the impact of social services on healthcare utilization and cost with the goal of identifying opportunities to invest in the social service infrastructure in Brooklyn. Objectives: Identify social services that impact healthcare utilization and cost and leverage findings to invest in services in Brooklyn that address social determinants of health. Methods: An analysis was conducted on a sample of 599 Medicaid patients engaged in at least nine months of consistent care management through the Brooklyn Health Home program during 2014. Patients in the sample who received social services during the study period were identified through a qualitative review of care management notes. Patients’ emergency room (ER) and inpatient utilization and costs for one year prior and one year following the receipt of service(s) were obtained from Medicaid claims data. Results: Findings from the pre-post analysis indicated reductions in ER and inpatient utilization and costs among patients who received housing, food assistance, income assistance, legal services, and vocational training interventions, and overall, the patients in the study experienced statistically significant (p<.001) reductions in number of ER visits, number of inpatient admissions, and ER-related Medicaid costs. Conclusions: Despite limitations of small sample sizes, the findings provide useful information about the impact of social service receipt on healthcare utilization and cost outcomes for high-need patients engaged in care management in Brooklyn. Public Health Implications: Based on research findings and a social service needs assessment in Brooklyn, MMC expanded an existing legal assistance clinic model to serve patients engaged with partners in the Community Care of Brooklyn (CCB) Performing Provider System (PPS) network. The intervention leverages a CCB training series, which prepares care managers and other providers to better recognize patients’ social needs and make appropriate referrals. The legal clinic provides patients with legal assistance services to address a variety of social determinants of health, including housing, food assistance, and income assistance issues.