Background: Aggressive care at the end-of-life can contradict patients’ wishes, negatively impact patient quality of life, and contribute to overall health care expenditures. Patients with mental disorders (MD) often experience disparities in medical care and have poorer clinical outcomes. We investigated the impact of mental disorders on emergency department (ED) use at the end of life among elderly patients with gastrointestinal (GI) malignancies. Methods: We conducted a retrospective cohort study using the SEER-Medicare database. We identified patients aged 66 years and older with GI malignancies (colorectal, pancreatic, gastric, hepatic, biliary, esophageal, small bowel, and anal cancer) diagnosed between 2004 and 2013 who had recorded death. We assessed the association between MD (depression, bipolar disorder, psychotic disorder, anxiety, dementia, and substance abuse) and ED use within 30 days of death using logistic regression models. Results: Of the 160,367 decedents included, 54,461 (34.1%) had at least one MD diagnosis between one year prior to cancer diagnosis and death. Those with MD were more likely to use the ED more than once in the last 30 days of life (14.7% vs. 12.4% p < 0.01). ED use was highest among decedents with anxiety disorder (15.8%) and substance abuse (16.3%). Among decedents with mental disorders, risk factors associated with ED use at end of life include being male (adjusted odds ratio [aOR] 1.16, 95% confidence interval [CI] 1.10 – 1.22), younger (aOR 1.14, 95% CI 1.06 - 1.23), and black (aOR 1.33, 95% CI 1.23 – 1.45), living in a lower income zip code (1.21, 95% CI 1.13 – 1.30), and having a higher Charlson comorbidity score (aOR 1.71, 95% CI 1.56 – 1.87). ED use was also associated with pancreatic (aOR 1.16, 95% CI 1.08 - 1.25), hepatic (aOR 1.21, 95% CI 1.11 - 1.33), biliary (aOR 1.16, 95% CI 1.03 - 1.30) and esophageal (aOR 1.16, 95% CI 1.04 - 1.29) cancer compared to colorectal cancer. Conclusions: MD is associated with increased ED use at the end of life among elderly patients with GI cancer. Palliative and supportive care including mental health services early in the disease course may improve quality of end-of-life care in this vulnerable population.