An 80-year-old man with severe anemia was found to have a circumferential type 3 lesion with obstruction in the gastric pylorus during upper gastrointestinal endoscopy. A contrast-enhanced CT scan of the abdomen showed severe invasion of the pancreatic head, and the diagnosis was gastric cancer L, Circ, cType 3, tub2, cT4b, N(+), M0, cStage ⅣA. The patient underwent laparoscopic gastrojejunostomy for gastrointestinal transit obstruction followed by 4 courses of SOX therapy as systemic chemotherapy. After chemotherapy, the invasion to the head of the pancreas was obscured, and pyloric gastrectomy and lymph node dissection were performed. The patient was recurrence-free as of 18 months after surgery. In this case, we performed gastric jejunal bypass surgery followed by chemotherapy with oral anticancer agents to achieve the downstaging of unresectable advanced gastric cancer with pancreatic invasion and pyloric stenosis in patients with poor general condition. As a result, the patient was able to undergo distal gastrectomy, which is one of the recommended multidisciplinary treatments.