Endoscopic sleeve gastroplasty (ESG) is performed by using endoscopic suctioning to reduce the volume of the stomach by plicating the greater curvature with an endoscopic suturing device or stapler. This allows for the endoscopist to perform an elective outpatient weight loss procedure. We will describe a single case of post-procedure day zero complication involving ESG resulting in ischemia, perforation, and peritonitis; what was discovered intra-operatively; and our operative management.