Introduction and importance Kommerell diverticulum is a very rare congenital defect of the aortic arch associated with the aberrant subclavian artery. It can present with signs of dysphagia, chest pain, or distal embolization in the upper limb. Case presentation We present a case of Kommerell diverticulum with associated large subclavian artery aneurysm in a male patient with chest pain of unknown origin and hypertension. There was an incidental finding of the wide mediastinum on chest X-ray and the patient had a difference in systolic blood pressure in both arms. A right thoracotomy incision was used to successfully excise the aneurysm and reconstruct the subclavian artery. Patient recovery was uneventful. Clinical discussion Endovascular approaches are also an alternative to conventional open surgeries in the treatment of Kommerell diverticulum. Conclusion Kommerell diverticulum with subclavian artery aneurysm should be considered in the differential diagnosis of non-cardiac chest pain. A simple investigation such as a chest X-ray can make a difference in these patients. Coarctation related to the right ASA might not always be a true coarctation. Endovascular treatment is an alternative to open repair in selected cases, but it needs further investigation in large randomized control trials.