Out-of-pocket spending on health care pushed over 10.5 million Americans into poverty in 2016. Medicaid helps offset this risk by providing medical coverage to millions of poor and near-poor children and adults and thereby constraining out-of-pocket medical spending. This article examines whether recent state-level expansions to the Medicaid program resulted in reductions in poverty and whether future changes to the program are likely to have similar impacts on poverty. Using a difference-in-differences research design, we found that the recent Medicaid expansion caused a significant reduction in the poverty rate. Moreover, by simulating a counterfactual poverty rate for a hypothetical world without Medicaid coverage, we found that the program's antipoverty impact grew over the past decade independent of expansion, by shielding beneficiaries from growing out-of-pocket spending. Future expansions or retractions of Medicaid are likely to produce associated effects on poverty.