Background: The standard treatment for locally advanced proximal gastric cancer invading the greater curvature is “open total gastrectomy combined with splenectomy” (OTG+S) aiming for whole clearance of the splenic hilar lymph nodes. However, its pertinent postoperative severe complication (e.g. pancreatic fistula) is problematic. An objective of this study is to evaluate the safety of “laparoscopic or robotic total gastrectomy with spleen-preserving splenic hilar dissection” (LRSHD) as a new treatment option which has a potential to reduce surgical morbidity, subsequently to replace the current standard treatment, OTG+S. Methods: This is a multicenter single-arm phase II trial. The main eligibility criteria are as follows; clinical T2-4a resectable locally advanced proximal gastric adenocarcinoma that invades the greater curvature; without obvious lymph node metastasis at the splenic hilum nor direct invasion to the spleen/splenogastric ligament. Protocol treatment is laparoscopic or robotic total gastrectomy with splenic hilar lymph node dissection (D2 + No.10 lymphadenectomy according to the Japanese guidelines) in which the spleen is preserved with skeletonizing the splenic vessels. Quality control of surgery is assured by surgeon’s qualification and central peer review of intraoperative photo at the splenic hilum after dissection. The primary endpoint is the proportion of postoperative pancreatic fistula and/or intra-abdominal abscess formation with Clavien-Dindo Grade III or higher (within 30 days after surgery). Secondary endpoints are intraoperative blood loss, operation time, mortality, overall postoperative complication, number of yield splenic hilar nodes, number of metastatic splenic hilar nodes, conversion to splenectomy, conversion to laparotomy, relapse-free survival, and overall survival. Sample size was set as 85 patients to obtain 80% power considering that 15% of patients are judged as unresectable intraoperatively, with the hypothesis that the primary endpoint would have an expected value of 7% and a threshold value of 16% in one-sided alpha of 0.1. Planned accrual period is 5 years. The accrual began in August 2019. As of August 2022, 53 of the planned 85 patients (62.4%) have been enrolled. When the safety of LRSHD is proved by this study, a non-inferiority phase III trial will be consequently launched. Clinical trial registry number: UMIN000037580. Clinical trial information: UMIN000037580.