Background: Ulcerative colitis (UC) is an immune‑mediated inflammatory disease that is associated with an increased incidence of cardiovascular events. Several inflammatory mechanisms associated with the pathogenesis of UC are involved in the initiation and progression of aortic aneurysms (AAs). We aimed to evaluate whether patients with UC have an increased risk of AA. Methods: We conducted a retrospective cohort study using data extracted from Taiwan’s National Health Insurance Research Database. All medical conditions for each case and control subject were categorized using the International Classification of Diseases, 9th Revision. Hazard ratios and 95% confidence intervals for associations between UC and AA were estimated using the Cox regression adjusted for comorbidities. Results: Our analyses included 7256 UC patients and propensity score‑matched controls. Compared to the controls, UC patients exhibited a significantly increased risk of developing an AA (adjusted odds ratio = 3.154, P < 0.001). Conclusion: UC patients have an increased risk of developing an AA, and healthcare professionals should be aware of this risk when treating UC patients. Aortic surveillance may be required for UC patients.