Peptic ulcer occurring in the gastric conduit for esophageal reconstruction sometimes penetrates into the mediastinal structures. We herein reported a case of pericardial penetration of gastric tube ulcer successfully treated with thoracoscopic pericardial drainage. A 66-year-old Japanese man, who had undergone esophagectomy for esophageal cancer 20 months before, visited our emergency room complaining severe back pain. Computed tomography revealed gastric tube ulcer penetrated into the pericardial space. Thoracoscopic pericardiotomy and drainage was performed and the patient made an uneventful recovery. Thoracoscopic pericardial drainage is useful to manage acute pyogenic pericarditis due to penetration of peptic ulcer which occurred in the gastric tube.