BACKGROUND: The age-specific risks of mortality for patients with esophagogastric cancer and their probability of surgical treatment are not well-known. METHODS: This population-based, nationwide cohort study included all patients with esophageal or gastric (esophagogastric) cancer in Sweden between 1990 and 2013, with follow-up evaluation throughout 2018. Age at diagnosis (exposure) was categorized into nine 5-year groups. The main outcome was 5-year all-cause mortality. The secondary outcomes were 90-day all-cause mortality, 5-year disease-specific mortality, 5-year disease-specific mortality excluding 90-day all-cause mortality, and non-operation. For mortality outcomes, Cox regression provided hazard ratios (HRs) with 95% confidence intervals (95% CIs) adjusted for confounders. For non-operation, logistic regression provided odds ratios (ORs) with 95% CIs. RESULTS: Among 28,725 patients, 11,207 (39.0%) underwent surgery. For those who underwent surgery, the HRs of 5-year all-cause mortality were stable before the ages of 65 to 69 years. After that, it gradually increased for patients 65 to 69 years old (HR, 1.13; 95% CI, 1.01-1.26), patients 75 to 79 years old (HR, 1.29; 95% CI, 1.56-1.44), and patients older than 85 years (HR, 1.84; 95% CI, 1.60-2.11) compared with those younger than 50 years. Analyses of age as a continuous variable, other mortality outcomes and stratification by comorbidity and tumor type showed similar results. The odds of non-operation increased for patients 75 to 79 years old (OR, 2.09 [95% CI, 1.84-2.94] for patients 80 to 84 years old and OR, 5.00 [95% CI, 4.31-5.78] for patients ≥85 years old or older), compared with those younger than 50 years. CONCLUSION: Older age, starting from 65 years, is associated with worse survival after surgery for esophagogastric cancer, and from 75 years with lower odds of surgical treatment.