Dental coverage for adults is an elective benefit under Medicaid. As a result of budget constraints, California Medicaid eliminated its comprehensive adult dental coverage in July 2009. We examined the impact of this policy change on emergency department (ED) visits by Medicaid-enrolled adults for dental problems in the period 2006–11. We found that the policy change led to a significant and immediate increase in dental ED use, amounting to more than 1,800 additional dental ED visits per year. Young adults, members of racial/ethnic minority groups, and urban residents were disproportionately affected by the policy change. Average yearly costs associated with dental ED visits increased by 68 percent. The California experience provides evidence that eliminating Medicaid adult dental benefits shifts dental care to costly EDs that do not provide definitive dental care. The population affected by the Medicaid adult dental coverage policy is increasing as many states expand their Medicaid programs under the ACA. Hence, such evidence is critical to inform decisions regarding adult dental coverage for existing Medicaid enrollees and expansion populations.