BACKGROUND: Filipinos have higher recurrence rates compared to other racial/ethnic groups, which might suggest a higher propensity for aggressive disease. The goal of this study was to perform a population-based analysis of disease extent at diagnosis and survival outcomes in Filipino patients with well-differentiated thyroid cancer relative to other racial/ethnic groups. METHODS: The study cohort comprised adult patients with well-differentiated thyroid cancer diagnosed between 2004 and 2015, identified in the California Cancer Registry. Rates of extrathyroidal extension, nodal metastasis, and distant metastasis were compared between Filipinos, Non-Filipino Asians, and Non-Asians using multilevel logistic regression models. Survival outcomes were compared using Cox regression models, utilizing a sequential modeling approach. RESULTS: Filipino ethnicity was associated with extrathyroidal extension (OR 1.35, 95% CI 1.11-1.63) compared with non-Asians and non-Filipino Asians. Filipino ethnicity was also associated with nodal metastasis (OR 1.32, 95% CI 1.18-1.46), and with worse OS (Hazard Ratio [HR] 1.45, 95% CI 1.20-1.75) and DSS (HR 1.51, 95% CI 1.12-2.04). After adjusting for demographic and clinical factors, Filipino ethnicity was no longer associated with OS (HR 1.03, 95% CI 0.84-1.25) or DSS (HR 0.93, 95% CI 0.68-1.28). CONCLUSION: Filipino patients with thyroid cancer are more likely to present with locoregionally advanced disease compared with non-Filipino Asians and non-Asians. Furthermore, Filipino patients have worse survival outcomes compared with non-Filipino Asians and non-Asians. However, this appears to be driven by the higher rates of locoregionally advanced disease in Filipino patients.