The indications for endoscopic full-thickness resection (EFTR) are limited because transmural communication during the entire procedure, causing tumor dissemination into the abdominal space, is inevitable. We invented a new method of EFTR without transmural communication, and explored its feasibility in an ex vivo porcine model. Three explanted porcine stomachs were used. First, markings around a model lesion were made with a flexible endoscope, and 0.9% normal saline with indigocarmine was injected into the submucosa around the markings. Second, a circumferential sero-muscular incision was made from the outside with an electrocautery knife, guided by the color of the submucosal injection and intragastric navigation with the endoscope. Third, the muscle layer was linearly sutured with the lesion inverted into the inside. Finally, a circumferential muco-submucosal incision was made with an electrocautery knife employed with the endoscope. The method was performed for 3 lesions (1 anterior wall, 1 lesser curve, and 1 posterior wall of the gastric body), and all lesions were successfully resected in en-bloc fashion. The mean size of the resected specimen was 4.5 cm in diameter. Neither perforation nor apparent air leakage was seen during or after the resection. Non-exposed endoscopic wall-inversion surgery (NEWS) is thought to be effective as a minimally invasive, and minimal-size endoluminal surgery for gastric submucosal tumors with or without ulceration, or even node-negative early gastric cancer that is difficult to resect by endoscopic submucosal dissection.