OBJECTIVE: To determine whether patients who are dual eligible for Medicare and Medicaid benefits have outcomes after carotid endarterectomy (CEA) that are comparable to the outcomes of those eligible for Medicare alone. METHODS: The study cohort included fee-for-service Medicare beneficiaries ≥65 years of age who underwent CEA (ICD-9-CM code 38.12) between 2003 and 2010. Beneficiaries with ≥1 month of Medicaid coverage were considered dual eligible. We fit mixed models to assess the relationship between coverage (dual eligible vs Medicare only) and outcomes over time after adjustment for demographic and clinical characteristics. RESULTS: There were 53,773 dual-eligible and 452,182 Medicare-only beneficiaries hospitalized for CEA. The percentage of dual-eligible patients receiving CEA increased from 10.1% in 2003 to 11.5% in 2010, with no change in geographic distribution across the country. In adjusted analyses, dual-eligible vs Medicare-only beneficiaries had a higher rate of 30-day ischemic stroke or death; higher in-hospital, 30-day, and 1-year all-cause mortality; and higher 30-day all-cause readmission. Relative annual reductions in outcomes from 2003 to 2010 ranged from 2% to 5%, but there was no significant interaction between dual-eligible status and time. CONCLUSIONS: Dual-eligible beneficiaries had worse outcomes than those eligible for Medicare alone. Additional work is necessary to understand the reasons for this difference.