Social determinants of health can adversely affect health and therefore lead to poor health care outcomes. When it launched in 2017, the Accountable Health Communities (AHC) Model was at the forefront of US health policy initiatives seeking to address social determinants of health. The AHC Model, sponsored by the Centers for Medicare and Medicaid Services, screened Medicare and Medicaid beneficiaries for health-related social needs and offered eligible beneficiaries assistance in connecting with community services. This study used data from the period 2015-21 to test whether the model had impacts on health care spending and use. Findings show statistically significant reductions in emergency department visits for both Medicaid and fee-for-service Medicare beneficiaries. Impacts on other outcomes were not statistically significant, but low statistical power may have limited our ability to detect model effects. Interviews with AHC Model participants who were offered navigation services to help them find community-based resources suggested that navigation services could have directly affected the way in which beneficiaries engage with the health care system, leading them to be more proactive in seeking appropriate care. Collectively, findings provide mixed evidence that engaging with beneficiaries who have health-related social needs can affect health care outcomes.