Anastomotic leakage is one of the common causes of serious morbidity and death after gastrectomy. The use of surgical treatment for leakage decreased due to the development of nonsurgical management. However, if nonsurgical management fails to control the spread of intra-abdominal infection, emergency surgical treatment is required. The authors wished to determine in which cases surgical treatment is needed for postoperative leakage and to identify treatment and prevention strategies. If a patient’s vital signs are stable, local abscesses can be cured by conservative treatment after percutaneous drain insertion; if there is no improvement in anastomotic leakage, endoscopic treatment such as clipping, vacuum, and stent placement can be performed. If a patient’s vital signs are unstable or patient shows diffuse peritonitis, surgical treatment should be performed. A surgical plan can be established according to leakage location. The duodenal stump may first require conservative treatment. It is recommended that surgical treatment be attempted first for anastomotic leakage of gastrojejunostomy site and gastric stump in remnant stomach. In conclusion, the need for surgical treatment is determined depending on vital signs and presence of diffuse peritonitis. During surgical treatment, a strategic approach is required according to the patient’s condition and the anatomical location of leakage.