<p>Endoscopic submucosal dissection (ESD) is a minimally invasive treatment for early gastric cancer that enables the en bloc resection of large lesions. However, it is associated with a significant risk of delayed bleeding, particularly in patients receiving antithrombotic therapy. Delayed bleeding after ESD causes anemia and serious systemic complications, including cardiovascular events. Here, we report a rare case of Takotsubo syndrome triggered by delayed bleeding after gastric ESD that culminated in cardiac arrest. A man in his 70s who underwent gastric ESD experienced delayed bleeding six days after the treatment, requiring emergency endoscopic hemostasis. The following day, the patient developed sudden ventricular fibrillation without prior chest symptoms. After resuscitation with electrical defibrillation, left ventriculography revealed apical ballooning consistent with Takotsubo syndrome. With intensive care, cardiac function recovered, and the patient was discharged ambulatory. Takotsubo syndrome is typically induced by stress, and often triggers psychological and physical stimuli. Although most patients present with chest pain or discomfort, our patient showed no preceding symptoms and developed sudden arrhythmia and cardiac arrest. This case highlights the need for aggressive bleeding prevention and enhanced post-ESD cardiac surveillance to mitigate rare but potentially fatal complications.</p>