Background: Red blood cell transfusions are common in patients undergoing gastrointestinal cancer surgery. Yet, to adequately balance their risks and benefits, clinicians must understand how transfusions may affect long-term outcomes. We aimed to determine if perioperative red blood cell transfusions are associated with a higher risk of all-cause and cancer-specific death among patients who underwent gastrointestinal cancer resection. Method: We identified a population-based cohort of patients who underwent gastrointestinal cancer resection in Ontario, Canada (2007–2019). All-cause death was compared between transfused and nontransfused patients using Cox proportional hazards regression, while cancer-specific death was compared with competing risk regression. Result: A total of 74,962 patients (mean age, 67.7 years; 55.4% male; 79.7% colorectal cancer) had gastrointestinal cancer surgery during the study period; 20.8% received perioperative red blood cell transfusions. Patients who received red blood cell transfusions had increased hazards of all-cause and cancer-specific death relative to patients who did not (hazard ratio: 1.39, 95% confidence interval 1.34–1.44; cause-specific hazard ratio: 1.36, 1.30–1.43). The adjusted risk of all-cause death was higher in early follow-up intervals (3–6 months postoperatively) but remained elevated in each interval over 5 years. The association persisted after restricting to patients without postoperative complications or bleeding and was robust to unmeasured confounding. Conclusion: Red blood cell transfusion among patients with gastrointestinal cancer is associated with increased all-cause death. This was observed long beyond the immediate postoperative period and independent of short-term postoperative morbidity and mortality. These findings should help clinicians balance the risks and benefits of transfusion before well-designed trials are conducted in this patient population.