Background and Purpose- We assessed ethnic differences in medication adherence 3 months poststroke in a population-based study as an initial step in investigating the increased stroke recurrence risk in Mexican Americans compared with non-Hispanic whites. Methods- Ischemic stroke cases from 2008 to 2015 from the Brain Attack Surveillance in Corpus Christi project in Texas were followed prospectively for 3 months poststroke to assess medication adherence. Medications in 5 drug classes were analyzed: statins, antiplatelets, anticoagulants, antihypertensives, and antidepressants. For each drug class, patients were considered adherent if they reported never missing a dose in a typical week. The χ2 tests or Kruskal-Wallis nonparametric tests were used for ethnic comparisons of demographics, risk factors, and medication adherence. A multivariable logistic regression model was constructed for the association of ethnicity and medication nonadherence. Results- Mexican Americans (n=692) were younger (median 65 years versus 68 years, P<0.001), had more diabetes mellitus ( P<0.001) and hypertension ( P<0.001) and less atrial fibrillation ( P=0.003), smoking ( P=0.003), and education ( P<0.001) than non-Hispanic whites (n=422). Sex, insurance status, high cholesterol, previous stroke/transient ischemic attack history, excessive alcohol use, tPA (tissue-type plasminogen activator) treatment, National Institutes of Health Stroke Scale score, and comorbidity index did not significantly differ by ethnicity. There was no significant difference in medication adherence for any of the 5 drug classes between Mexican Americans and non-Hispanic whites. Conclusions- This study did not find ethnic differences in medication adherence, thus challenging this patient-level factor as an explanation for stroke recurrence disparities. Other reasons for the excessive stroke recurrence burden in Mexican Americans, including provider and health system factors, should be explored.