A 56-year-old woman visited our hospital for the evaluation of a subepithelial lesion in the upper esophagus that was found during a screening endoscopy. She did not demonstrate any associated symptoms, such as dysphagia or weight loss, and she denied a family history of gastrointestinal cancer or a history of previous surgery. Upper endoscopy revealed a pulsating lesion, covered with esophageal mucosa, on the posterior side of the upper esophagus (Fig. 1A). On endoscopic ultrasonography, a dilated vessel connected to the right-side aortic arch is seen at the site of the lesion (Fig. 1B). Enhanced computed tomography demonstrated compression of the esophagus by the trachea, the right-side aortic arch, and an aneurysmal dilated vessel (Fig. 2A). Computed tomography angiography revealed the aberrant left subclavian artery, connected to the right-side aortic arch, as the origin of the aneurysmal dilated vessel (Fig. 2B). Therefore, the subepithelial lesion in the upper esophagus was diagnosed as Kommerell’s diverticulum, the aberrant left subclavian artery originating from the right-side aortic arch, causing an extraluminal compression.