In the twenty-three states that have decided against expanding Medicaid under the Affordable Care Act, uninsured adults who would have been eligible for Medicaid and have incomes at or above the federal poverty guidelines are generally eligible for Marketplace (insurance exchange) premium tax credits and plans with generous benefits. This study compared estimated out-of-pocket spending for care and premiums, as well as the financial burdens they impose, for the families of these adults under two simulation scenarios: obtaining coverage through a silver plan with subsidized cost sharing and enrolling in expanded Medicaid. Compared with Marketplace coverage, Medicaid would more than halve average annual out-of-pocket spending ($938 versus $1,948), while dramatically reducing the percentage of adults in families with out-of-pocket expenses exceeding 10 percent or 20 percent of income (6.0 percent versus 17.1 percent and 0.9 percent versus 3.7 percent, respectively). Larger reductions would be seen for families with smokers, who under Medicaid would no longer be subject to Marketplace tobacco user surcharges. Medicaid expansion may offer a greater opportunity than access to Marketplace insurance to promote the financial well-being of previously uninsured low-income adults.