AbstractSeveral reconstruction methods are used in proximal gastrectomy. Esophagogastrostomy is the simplest and most physiological. The challenge in esophagogastrostomy is preventing reflux esophagitis. Various techniques have been developed to reduce reflux of gastric juice. Taking advantage of the usefulness of the recently reported modified side overlap with fundoplication by Yamashita (mSOFY) method, we developed a y‐shaped mSOFY method that is simpler and has potential for a greater anti‐reflux effect. Unlike the original mSOFY method, the pseudo‐fornix does not go behind the esophagus and the axes of the esophagus and residual stomach are shifted by approximately 60° to form a “y” shape. In addition, fixation of the residual stomach and both sides of the esophagus and crus of the diaphragm is performed at the end of the procedure. We performed 12 cases of laparoscopic or robotic proximal gastrectomy with y‐shaped mSOFY esophagogastric anastomosis located below the crus of the diaphragm for gastric or esophagogastric junction adenocarcinoma between August 2021 and March 2023. The median operative time and blood loss were 260 min and 5 mL, respectively. No postoperative complications of Clavien–Dindo classification grade II or higher occurred. No stenoses requiring balloon dilation occurred within 1 year after surgery, but endoscopy at 1 year after surgery revealed two cases (17%) of reflux esophagitis of Los Angeles grade B or higher. In conclusion, this y‐shaped side overlap esophagogastrostomy method could be one of the recommended esophagogastrostomy procedures in proximal gastrectomy.