Improvements in therapeutic modalities have prolonged the survival of gastric cancer patients. Comorbidities such as thromboembolic events that emerge as a result of disease complexities and/or treatments received have not been considered. The objectives of this study are to examine the relationship between gastric cancer and ischemic stroke, and to determine predictive risk factors. A nationwide population-based cohort study was conducted using data from the Taiwan National Health Insurance database. A total of 45,060 gastric cancer patients and non-cancer counterparts without antecedent stroke were recruited. Hazard ratios (HRs) and the cumulative incidence of ischemic stroke were calculated, and risk factors for ischemic stroke were assessed. Gastric cancer patients were associated with higher risk of ischemic stroke (HR 1.11, 95% confidence interval [CI] 1.03-1.19, P = 0.007), especially in participants younger than 65 years (HR 1.61, 95% CI 1.39-1.86, P < 0.001) and in female participants (HR 1.30, 95% CI 1.14-1.49; P < 0.001) when compared with the matched cohort. Independent risk factors of ischemic stroke in gastric cancer patients included age, hypertension, atrial fibrillation, dyslipidemia, and having received major surgery for gastric cancer. Our findings suggest the importance of stroke surveillance and prevention strategies in high-risk patients. Having received major surgery for gastric cancer is a significant risk factor in these patients.