Objective: Social determinants of health (SDH) have been shown to correlate with adverse cancer outcomes. It is unclear if their impact goes beyond behavioral risk or healthcare access. We aimed to evaluate the association of SDH with endometrial cancer outcomes in a public healthcare system. Design and Setting: A retrospective cohort study of endometrial cancer patients in Ontario, Canada. Population: Women diagnosed with endometrial cancer in Ontario between 2009-2017. Methods: Clinical and sociodemographic variables were extracted from administrative databases. Validated marginalization scores for material deprivation, residential instability and ethnic concentration were used. Associations between marginalization and survival were evaluated using log-rank testing and Cox proportional hazards regression. Results: 20228 women with endometrial cancer were identified. Fewer patients in marginalized communities presented with early disease (70% vs. 76%, p