Endoscopy is an important noninvasive procedure for patients with gastrointestinal problems. However, surgical techniques are shifting to laparoscopic surgery, and changes in endoscopic findings after laparoscopic surgery differ from those after previous surgical methods. Postoperative endoscopic findings differ from normal anatomical structures, and findings reportedly vary depending on the type of surgical technique. Therefore, we aimed to summarize the surgical and endoscopic findings for each surgical method from the surgeon's point of view. The causes of gastric emptying delay, bleeding, afferent loop syndrome, or anastomosis leakage occurring after gastric cancer surgery can be identified via upper gastrointestinal endoscopy that is relatively less invasive than the surgical method. Regarding postoperative anastomosis leakage, endoscopy can directly evaluate the degree of leakage at the anastomosis site more accurately than computed tomography and enable immediate intervention. As endoscopy is less invasive than the surgical method, patients can be evaluated and treated more safely. However, coordination between the surgeon and the endoscopist is necessary to perform the procedures effectively. Therefore, reviewing the changes in surgical and endoscopic findings is important.