BACKGROUND: The National Institutes of Health has advocated for improved minority participation in clinical research, including clinical trials and observational epidemiologic studies since 1993. An understanding of Mexican Americans (MAs) participation in clinical research is important for tailoring recruitment strategies and enrollment techniques for MAs. However, contemporary data on MA participation in observational clinical stroke studies are rare. We examined differences between Mexican Americans (MAs) and non-Hispanic whites (NHWs) participation in a population-based stroke study. METHODS: We included 3,594 first ever stroke patients (57.7% MAs, 48.7% women, median [IQR] age 68 [58-79]) from the Brain Attack Surveillance in Corpus Christi Project, 2009-2020 in Texas, USA, who were approached and invited to participate in a structured baseline interview. We defined participation as completing a baseline interview by patient or proxy. We used log-binomial models adjusting for prespecified potential confounders to estimate prevalence ratios (PR) of participation comparing MAs with NHWs. We tested interactions of ethnicity with age or sex to examine potential effect modification in the ethnic differences in participation. We also included an interaction between year and ethnicity to examine ethnic-specific temporal trends in participation. RESULTS: Baseline participation was 77.0% in MAs and 64.2% in NHWs (Prevalence Ratio [PR] 1.20; 95% CI, 1.14-1.25). The ethnic difference remained after multivariable adjustment (1.17; 1.12-1.23), with no evidence of significant effect modification by age or sex (Pinteraction by age = 0.68, Pinteraction by sex = 0.83). Participation increased over time for both ethnic groups (Ptrend < 0.0001), but the differences in participation between MAs and NHWs remained significantly different throughout the 11-year time period. CONCLUSION: MAs were persistently more likely to participate in a population-based stroke study in a predominantly MA community despite limited outreach efforts towards MAs during study enrollment. This finding holds hope for future research studies to be inclusive of the MA population.